Cuaderno-13-Human-Ecology-of-a-Species-Introduction-Interactions-between-Humans-and-Introd

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Human Ecology of a Species Introduction: Interactions between Humans and Introduced

Green Iguanas in a Puerto Rican Urban Estuary

By: Carlos G. García-Quijano1,2 and Tomás A. Carlo-Joglar3

1Assistant Professor, Department of Sociology and Anthropology,

University of Rhode Island 2Research Associate, Instituto de Investigaciones Interdisciplinarias,

Universidad de Puerto Rico-Cayey 3Assistant Professor, Department of Biology, Pennsylvania State University

With the collaboration of Mario Flores-Mangual, Jorge Bauzá, Héctor Martínez, Natalia Rodríguez, and Javier Arce

TABLE OF CONTENTS

Acknowledgements.................................................................................................... 1 Introduction................................................................................................................ 2 Species Introductions are Human Ecological Phenomena ........................................ 3 Brief history of the green iguana introduction........................................................... 11 Iguanas were significantly aggregated towards the borders of the mangrove forests 16 There was a spatial association between human settlements and iguana populations 17 Structured intercept interviews with SBJE recreational and subsistence resource users 22 Attitudes towards exotic species and the green iguana ............................................. 23 Conclusion ................................................................................................................. 34 References.................................................................................................................. 36

Acknowledgements:

We would like to thank Mario Flores-Mangual, Jorge Bauzá, Natalia Rodríguez,

Héctor Martínez, Augusto Carvajal, Javier Arce, and Emmanuel Rivera for their help

during research design, data collection, data analysis, and dissemination. We also thank

Hilda I. Lloréns for useful editorial advice and suggestions, as well as Isar Godreau and

Jorge Bauzá for financial and logistical support. The fieldwork reported herein was made

possible by a grant from the San Juan Bay Estuary Consortium to T. Carlo-Joglar, C.

García-Quijano and M. Flores-Mangual; and from a seed-money grant from the Instituto

de Investigaciones Interdisciplinarias, UPR-Cayey, to C. García-Quijano. Responsibility

for any shortcomings of this report rests with the authors C. García-Quijano and T. Carlo-

Joglar. Finally, we would like to thank everyone who took time from their busy schedules

to talk to us during our field interviews.

Introduction

Non-indigenous, introduced species and their impact on invaded ecosystems are a

worldwide concern (Vitousek et al. 1996; Temple 1990; Pfieffer and Voeks 2009). By

some accounts, introduced species pose one of the greatest current threats to the global

environment, similar in magnitude to industrial pollution and global warming. Although

globalization, and the increased interconnectedness of human populations and economies

have certainly accelerated species introductions and associated alarm by people and

governments in the last few decades, concern for introduced species is not new: spirited

debates about introduced and exported plants and animals have been raging for over a

century in both sides of the Atlantic Ocean (Coates 2007; Elton 1958; Howard 1897).

When a species of organism is introduced to a new geographic area, it becomes

subject to interactions with the biotic and abiotic components of the local ecosystem,

including humans who live in the area. The nature of these interactions will determine

whether the species will become established or not, and whether the new species will

have a minor or major impact in the structure of the host ecosystem. In particular,

interactions with humans will also determine whether the new species will be classified

as beneficial, harmless, a nuisance, or hazardous, and thus what course of action and

policy will be taken in respect to the introduced species. In other words, the introduced

species’ interaction with the dominant species in the ecosystem –humans– will be crucial

to the trajectory and the fate of the introduced species and its surrounding ecosystem.

This paper reports results of ongoing interdisciplinary research about the

interactions between people and an introduced large arboreal lizard (the green iguana,

Iguana iguana) in the San Juan Bay Estuary (SJBE), located in the Caribbean island of

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Puerto Rico. Green iguanas have become established in Puerto Rico’s coastal and

riparian forests since having been introduced to the island by pet enthusiasts beginning as

early as the 1970’s. As evidenced by a large amount of Puerto Rican newspaper press

dedicated to the subject, the green iguana, along with the small Indian mongoose

(Herpestes javanicus), the Patas monkey (Erythrocebus patas), the rhesus macaque

(Macaca mulatta), and the spectacled cayman (Caiman crocodilus) have become one the

most talked and written-about new exotic additions to Puerto Rico’s vertebrate fauna

(notwithstanding that feral domestic cats, dogs, and rats, all of which have become feral

in Puerto Rico, each vastly outnumber and “out-impact” any other introduced vertebrate

species).

Species introductions and their impacts in populated coastal areas are multi-

dimensional phenomena that transcend traditional scientific discipline boundaries. The

research presented herein is part of an ongoing interdisciplinary research project that

combines ecological and anthropological approaches to characterize the green iguana’s

impact on and Puerto Rico’s estuaries and coastal forests. The ecological and

sociocultural aspects of the green iguana introduction to Puerto Rico’s coastal forests are

intrinsically linked. An increased understanding of the origins, causes, effects, impacts,

and future trajectories of human-mediated species introductions must come from

collaborations between the social and ecological sciences.

Species Introductions are Human Ecological Phenomena

A species introduction is generally defined as the human-mediated move of floral

or faunal species to an ecosystem or landscape where the species would not be present

were it not for human intervention (Carlton 2001). Although the vast majority of research

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regarding species introductions is done in the biological sciences, species introductions

are by definition a human ecological phenomena, tied in origins, proximate and distal

causes, effects, and outcomes to human activities, cultural values, and socioeconomic

factors.

The fossil, archaeological, and historical record shows that when Homo sapiens

move from place to place, they almost invariably transport other fauna and flora species

with them (Reitz and Wing 2008:116; Vermeij 2005). The earliest recorded non-native

species introduction by humans is the introduction of the gray cuscus (a small marsupial,

Phalangys orientalis) from New Britain to New Ireland in the Papua New Guinea

Archipielago, about 19,000 years ago (Allen and White 1989; Grayson 2001; Flannery

and White 1991). Tools, clothing, and transportation vessels provide more places where

other organisms can “catch a ride” with moving humans. The domestication of plants and

animals meant that traveling humans would come to depend on –as well as develop

whole subsistence/cultural systems about– certain plant and animal species. These

species of plants and animals would likely be transported by people when they moved to

new areas, whether already populated or not. Introduced agricultural species that are

important for human subsistence can become iconic or sacred species in the host location,

even after a relatively short time since introduction (Fowler 2005).

The long-standing association between people and the plants and animals they

depend on for food, tools, shelter, or companionship is so strong that changes in faunal

assemblages (the presence of novel or newly abundant organisms in the archaeological

record) are often used by archaeologists as proxies to reconstruct the movements of

people across space and time. For example, direction and timing of human settlements in

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the Caribbean Archipielago by early island settlers have been partly traced by looking at

the animals and plants that the settlers brought with them as they moved from the

American continental masses to the islands and between islands (Newsom and Wing

2004; Rouse 1992; Wilson 1997; Wing 1989). Similar lines of evidence have been used

as evidence to reconstruct people movements in the insular Pacific and Indian Oceans

(Nowak 1999; Crosby 1986; Reitz and Wing 2008:317). However, because species also

migrate and move by non-anthropogenic forces, it is often hard to tell whether novel

species have appeared in a location by human mediation or by non-human processes

(Wing 1993).

As the world has become more connected during the last 5 centuries (i.e. more

people and goods have moved more between previously unconnected regions of the

world), species introductions by people have accelerated exponentially. Agricultural and

animal husbandry species such as wheat, maize, tomatoes, chickens, cattle, horses,

sheep/goats and pigs have been propagated through most of the range of human

habitation. The same has happened with animal companions/workers such as dogs and

cats and also with unwanted pests or hitchhikers such as rats and house mice, which have

traveled with humans to virtually every place that humans have settled-except possibly

the Artic Circle. Thus whether a species introduction happens and whether it will happen

again on the future often depends on socioeconomic factors extraneous to the workings of

local ecosystems (and even local societies). For example, centuries ago the contact

between the Old and New Worlds propelled hundreds or thousands of species in both

directions of the Atlantic. More recently, the Green and Blue Revolutions have exported

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economically important species (as well as many of their symbionts) to worldwide

distributions.

The exotic animal trade is another source of the translocation of species to foreign

locales. Exotic animals have long been commodities and symbols of wealth, power, and

prestige. Trade in exotic animals for companionship, entertainment, or prestige is

millennia old: for example, one of ancient Egyptian King Ptolemy ii’s most prized

possessions was a live polar bear and which led precessions through the streets of third

century B. C. Alexandria (Bruemmer 1998). Marco Polo described how Kublai Khan

traveled with an extensive raptor collection that featured falcons and gyrfalcons from

several continents (Bruemmer 1998). This is not confined to the Old World: there is

prehistoric evidence of a large, organized trade in macaws (Ara sp.) from tropical

(southern) Mexico to the American Southwest that included extensive keeping and

breeding facilities along the way –a trade that continues today- (Hargrave 1970; Minnis

et al. 1993). The modern exotic pet trade is a huge worldwide enterprise that involves

people from all socioeconomic backgrounds. This trade is the source of several high-

profile species introductions such as Burmese pythons in Florida and caymans in northern

Puerto Rico, as well as (at least partly) the green iguanas.

Social science work on species introductions has revealed that people’s

perspectives and attitudes towards introduced species (and whether they are considered as

a “natural” part of the ecosystem or not) vary depending on the specific impacts that the

species has on their livelihoods enjoyment of the landscape and their sense of

environmental aesthetics, phylogenetic bias, knowledge of and experience with their local

ecosystems, (Pfeiffer and Voeks 2008; Fortwanlger 2009; Hall 2009; Weeks and Packard

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2009). We found during this research that another source of variation can be the extent to

which any nationalistic pride sentiments extend to people’s attitudes and values towards

their environment-as is the case in Puerto Rico and much of Latin America-.

Only a tiny minority of the plants or animals that are introduced to a new

ecosystem are able to produce permanent populations; some of them however can

explode and radically impact the host ecosystem over time. Some introduced plants and

animals have been reproducing in their host ecosystem for so long that most people who

live there do not recognize them as introduced by people: to them the introduced species

is a part of their surrounding ecosystem as much as any other local species.

Anthropologists have provided important insights on this: For example, Fortwangler

(2009) documented how residents of the island of St. John, USVI, regarded long

introduced wild donkeys as part of their island ecosystem; these island residents were in

turns surprised and dismayed when the National Park Service started a campaign of

eradication that included hunting down and killing donkeys. Similarly, Weeks and

Packard (2009) report that while park rangers and scientists working at the Beg Bend

National Park in Texas tend to view introduced feral hogs as unwanted invasive species’,

many long-time residents’ of the park’s area regard hogs as “nature’s bounty”, a valued

resource to be used and perhaps managed and protected by people. Similar variation in

attitudes towards an introduced plant species is found in a study by Hall (2009).

In both the St. John’s and Big Bend cases, people who had for generations

inhabited the island had ideas of what species were “natural” for their ecosystem, based

on their experience and collective memory, that were radically different from government

ecologists and resource managers who based their assessments on notions of

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biogeography and the geologic record. A whole society’s overall interactions with and

attitudes toward introduced species can also change over time, sometimes oscillating

several times between mostly favorable and mostly unfavorable as the species

introduction unfolds (Coates 2007).

As Pfeiffer and Voelks, (2009) show in their exhaustive review of human

interactions with introduced species, local peoples’ experiences with introduced species

are widely varied, ranging from disasters resulting in ecosystem disturbance, loss of

biodiversity and loss of livelihoods (e.g. Nile Perch in Lake Victoria; Goldsmidcht 1999)

to relatively small ecological impacts coupled with new economic opportunities (e.g. Hall

2009). In some cases, even reviled introduced species such as the zebra mussel have even

improved environmental quality in eutrophic lakes, benefiting endemic fish populations

(Reed-Andersen et al. 2000; Reeders and Bij de Vaate 1990).

Pfeiffer and Voeks (2009) developed a useful typology of introduced species

based on their interactions with humans and their cultural systems. They defined

‘culturally invasive’ biota as “non-native organisms or genetic material that have

ecologically displaced or extirpated native biota, resulting in a detectable cultural impact

on resident societies” (page 2). They further categorized introduced species, based on

their interactions with resident human groups as either culturally impoverishing’,

‘culturally enriching’, or ‘culturally facilitating’ (page 2).

Even conservation-minded ecological scientists vary in their attitudes, and values

towards introduced species. While some view species introductions in general as a great

threat to the integrity of ecosystems worldwide, others advocate regarding species

introductions and their effects on ecosystems on a case-by-case basis. In a debate in the

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journal Conservation Biology between 1990 and 1992, three influential ecological

scientists (Stanley Temple, Ariel Lugo and Bruce Coblenz) presented opposing views of

the role people and policy should play in confronting introduced (called “exotic” in the

debate) species. In an editorial titled: “Eradicating Exotics: A Nasty Necessity”, Temple

(1990) argued that a deal of human resources and effort should be directed to eradicating

exotic species from places where they might be creating problems for native species.

Ariel Lugo responded a in a letter to the editor a few months later (Lugo 1990), stating

that removal of established exotic species is often a complex undertaking of uncertain

results and dubious chances of success, that no species should be seen as inherently evil

or harmful just because it wasn’t native to that location, and that an assessment of

harmfulness or beneficence should be done empirically (Lugo 1990). Bruce Coblenz

weighed in to align himself mostly with Temple’s position. The journal-based debate got

quite heated: Lugo was accused of having a “cornucopian view” of nature, a statement he

apparently took offense to in a later response (Lugo 1992).

One of the striking features of the short public debate scribed above is that while

the authors presented quite opposing views about introduced species, they were all

concerned with and defending healthy ecosystem functions and biodiversity and they

based their opinions on what each deemed was good scientific evidence. What they

differed about was their appreciation of which species should be allowed to be part of a

given ecological community, i.e. what makes a species a suitable member of the

community.

The focal point of these and similar debates (e.f. Sagoff 2003; Simberloff 2003;

Subramanian 2008) and disagreements is the different actors’ appreciation of what

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constitutes a valid ecological community. Benedict Anderson used the term “imagined

communities” to describe the historically-recent rise of nationalism as a powerful

political and ideological force in worldwide politics (Anderson 1983). For Anderson, the

modern nation is an example of an “imagined’ political community because people of the

same nationality conceive themselves as a bounded community distinct from others and

united by a measure of comradeship, even though they will never have any kind of

interaction with the vast majority of fellow nationals and despite the fact many of these

nationals are their competitors or even their oppressors.

The ‘imagined communities’ concept has important implications for this analysis.

By accepting that the boundaries that define a community are, to an extent, imagined, the

possibility opens up that people might have competing ideas of what the community’s

membership is or should be, where the boundary between a community and the next one

should lie, and what type of boundary it should be. What people call “ecosystems” are by

and large really open, dynamic entities. However, the mere use of the word system

implies a border of some fashion inside of which lie the components of the system and

outside of which are non-system entities. Categorization, classification, and the drawing

of boundaries are essential to understanding the world by reducing the vast complexity of

the world to manageable amounts of information. Where and how such boundaries (for

example between the “natural” and “non-natural” distributions of an organism) are

drawn, however, is a decision made by people based on criteria, preferences, needs, and

values that are often culturally shared and mediated.

Whether or not a novel species is accepted by people, and specially by local

ecological scientists, as a “natural” or “naturalized” component of the system, is not a

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trivial issue: if a species believed to be “introduced” or “exotic” also is also put in the

category of potentially “harmful”, or “invasive”, it can lead to expensive, laborious, and

even ecologically destructive (Bergstrom et al. 2009; Cadotte 2009) eradication

initiatives. Conversely, any species that becomes established in a novel ecosystem will

initiate some changes, and people will be better able to take effective action if they have

an accurate idea of the interactions happening as a result of the novel species’ activities.

We are of the opinion that species introductions and their life histories are

complex phenomena, influenced by both socio-cultural and ecological factors.

Interdisciplinarily-conceived studies and analyses (not mere combinations of methods)

are necessary to truly understand species introductions and to inform environmental

policy. In the rest of this article we will present some findings of our research about

people-green iguana interactions in the San Juan Bay Estuary in Puerto Rico, as well as

some of the implications for policy regarding this and other similar species introductions.

Brief history of the green iguana introduction

Biology and Natural History of the Green Iguana

Iguana iguana is a large and widely distributed arboreal lizard from the Neotropics,

ranging in distribution from México and the Caribbean, to northern Argentina in South

America (Schwartz & Henderson 1991). It is sexually dimorphic, with the males being

larger and more ornamented than females (Rivero 1998). Mature males can reach a

length of two meters and a weight of over 15 pounds. Iguanas reach sexual maturity at

about 16 months and large females can lay over 60 eggs. The nest site needs to remain at

30 °C, and is often located in exposed sandy or loamy substrate (Rivero 1998). The green

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iguana is considered a social reptile species with individuals gathering in locations for

feeding, reproduction, and thermoregulation (Phillips et al. 1993).

Green iguanas are distinguished form other lizards in that they are uniquely adapted

to herbivorous and arboreal life (Hirth 1963, Troyer 1984, Britton 2002). Green iguanas

possesses small, evenly sized, sharp teeth that are unique among reptiles because they are

specially shaped to easily cut leaves (Montanucci 1968, King 1996). They have extra

long toes that allow them to easily climb and walk trough tree canopies and branches.

They digest tough cellulose and other plant material by hind-gut fermentation even at the

juvenile stages of their life (Troyer 1984, 1984a, King 1996, Britton 2002). Although

most substantiated accounts of green iguana diets in the wild show that green iguanas are

fully or almost fully herbivorous, the composition of the green iguana’s diet, specifically

whether they are just herbivores or omnivores that represent a predatory danger to Puerto

Rican island fauna, is a controversial topic for the popular press and conservation sectors

in the island (e.g. Cedeño 2009).

Green iguanas have long been a food resource for people throughout their original

range in Central and South America. For thousands of years, iguanas have been hunted as

well as kept and raised by people for their meat (Benson 1977; Coe and Flannery 1967).

In Puerto Rico it’s been widely known for years that people in Central and South

America eat green iguanas and that “gallina de palo” (tree chicken), one of the names by

which the green iguana is known in Central America, refers both to the iguana meat’s

chicken-like quality and its importance as a staple food item.

Green iguanas are also popular pets and figure importantly in the modern live

reptile trade. They are easily tamed and breed well in captivity. The Smithsonian

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National Zoo reports that 800K green iguanas were imported into the United States in

1995 alone. Numerous websites are dedicated to green iguana pet keeping, care, and

reproduction. The modern pet-shop based trade in green iguanas in the US dates at least

back to the 1960’s, but there was a great surge in pet trade popularity for iguanas and

other prehistoric-looking reptiles in the mid-late 1990’s that has been attributed to an

increase in people’s interest in such reptiles after the release of the Hollywood

blockbuster movie “Jurassic Park” (Christy 2008).

Iguanas began to be regularly spotted in the estuaries near San Juan, Puerto Rico’s

capital and most populous county in the between the 1980s and 1990’s, and by the early

2000’s several government agencies and news media channels began to regularly address

the increasing green iguana populations in Puerto Rico. Several of our informants

reported that wild green iguanas have been established in parts of eastern Puerto Rico for

several decades. Interestingly, while it seems clear that the trade in pet green iguanas is

largely responsible for the recent explosion in green iguana populations in Puerto Rico,

there is still speculation, based on some historical and genetic evidence, that waves of

green iguanas might have been reaching the Virgin Islands and possibly Puerto Rico over

the years by a combination of rafting and introduction by humans (Stahl 2009).

In 2007 Jorge Bauzá, the science coordinator of the San Juan Bay Estuary

Consortium (SJBE) and authors Carlo-Joglar and García-Quijano designed a program for

the interdisciplinary monitoring of green iguanas and their interactions with human and

non-human components of the estuary’s ecosystem. The SJBE is a consortium of federal

agencies, Puerto Rican state agencies, and NGO’s with the common objective of

coordinating research, education, and resource management in the largest mangrove

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estuary in Puerto Rico. The goal of the sociocultural component of this research was to

explore Puerto Ricans’ attitudes, values, and knowledge about introduced species with

emphasis on the green iguana, to provide a description of the interactions between people

and green iguanas in the SBJE, and to develop a framework to collaborate with SBJE

residents and resource users in monitoring of introduced iguana populations.

In the rest of this article, we will describe some remarkable findings of our

research about the interactions between green iguanas and people in the SJBE. Because

we used varied methods and approaches for different research questions, the relevant

methods will be detailed in each section. The results of the wildlife ecology component

of our research can be found in our technical report to the SJBE (Carlo-Joglar and

García-Quijano 2008) and are being prepared for submission to appropriate thematic

journals.

A. The spatial association between human activities and green iguana populations

One of our principal fieldwork activities consisted in mapping the distribution of

green iguana populations in the SBJE region to assess the spatial abundance patterns of

iguanas in the estuary. We wanted to assess approximately how many iguanas were living

in the SBJE, in which parts of the estuary they were concentrated (and thus more likely to

cause an impact), what resources were the iguanas utilizing, and what features of the

ecosystem would be good predictors of iguana concentrations.

We conducted a landscape-scale adult iguana census in the mangroves of the

SJBE from May through August of 2008. Navigation with a small boat and kayaks was

used to count iguanas at edges of lagoons. Transects on foot were established to count

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iguanas inside mangrove forests far from edges (at least 100 m from the nearest edge),

and on non-mangrove secondary growth vegetation bordering mangrove forest.

Observers worked in pairs, with one person watching, and the other recording the data.

Once an iguana was detected, we recorded the spatial coordinates of iguana location with

a handheld GPS For each location, we recorded the # of iguanas per tree, tree species,

and a category of the degree of defoliation of the tree, if any was observable. All

defoliated trees were mapped regardless of the presence of iguanas since they may

represent unseen animals or previous iguana aggregations.

We performed an Ordinal Logistic Regression Analysis of iguana detections

(presence or absence) as a function of distance to the 1) nearest vegetation edge (i.e., non-

mangrove vegetation such as pasture, scrubland, secondary forest, etc.), and 2) the distance to

the nearest human settlement (house, buildings, etc.). This procedure consisted of randomly

generating sampling points over the iguana distribution map, using the random points to

locate the nearest sampling transect location, and from there measuring distance to edges and

urban structures, and whether iguanas were detected in the vicinity.

Iguanas were not distributed randomly across the SJBE (figure 1). We found that

both the distance to nearest vegetation edge (r2=0.25, p<.0001), and the distance to the edge

human settlements ((r2=0.29, p<.0001) were good predictors of the probability of sighting

iguanas in mangroves, with the distance to urban edges being a slightly better predictor

(Figure 1). These two clear trends in the spatial aggregation patterns of green iguanas in the

SBJE are highly relevant to our discussion of human-introduced species interactions. They

are detailed below:

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Iguanas were significantly aggregated towards the borders of the mangrove forests

We found a total of 1625 adult iguanas (Table 1), of which 97.6% were found on

trees at the edges of lagoons, channels, and bays. On the other hand, the number of iguanas in

mangrove forest away from edges was 0.20%. Non-mangrove forests were not well

represented because they were rare and only a proportionally small region was sampled in

Piñones for about 1 % of the iguanas. Two of the largest mangrove lagoons in the SJBE,

Torrecilla and Caño Martín Peña lagoons (see figure 2), contained 85 % of all iguana records

but represented only 42 % of the linear distance of the surveys. Iguanas were virtually absent

away from edges and were rare in pure mangrove patches in these lagoons and elsewhere,

with only 3 iguanas detected in within-mangrove transects.

This finding has important implications regarding people’s perceptions of the

severity and impacts of the green iguana populations in the SJBE. First, the vast majority

of people who visit or pass by the SJBE’s mangrove forests only observe the forest edge

areas of the estuary rather than the inner forest areas. This can create an illusion of

abundance because the part of the mangrove that people are observing is precisely where

green iguanas are disproportionately concentrated. Were casual observers to penetrate the

forest just a few meters, they would find that green iguanas are far from abundant in the

vast majority of the mangrove forest. In other words, people that are just observing the

forest edges might form an erroneous mental image of a forest packed with green

iguanas.

The second implication is that green iguanas are probably having a less severe

impact on ‘climax’ mangrove forests than what both laypeople and environmentalists

might have feared. A highly successful multi-sector educational campaign about the

value (intrinsic and practical) of mangrove forests for Puerto Ricans has educated many

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Puerto Ricans to view mangroves as treasured natural resources rather than sources of

pestilence and mosquito-borne diseases, especially malaria, as they were viewed during

much of the 20th century. Thus, one of the principal sources of concern about the green

iguana introduction was related to the impacts that iguanas might have on mangrove

forests. Our findings suggest that iguanas can have significant impacts on localized

mangrove stands near forest edges, but by and large, the majority of mangrove forests are

not being impacted. In contrast with the less diverse inner forest, mangrove forest edge

areas usually contain not just mangrove trees, but a combination of mangroves with other

types of trees along with grasses, shrubs, and vines.

There was a spatial association between human settlements and iguana populations.

This is consistent with what is known about many species introductions: that

because of the profound effect that human activities can have on the landscape, one of the

most important characteristics that a potentially invasive species (introduced or native)

can have is its ability to adapt and thrive in proximity to humans and human-caused

changes. For example, one of the reasons why the English Sparrow was able to establish

large populations across the continental United States after its introduction in the East

Coast was that it was able to exploit two abundant and predictable resources: human

garbage and undigested seeds in carriage horse droppings (Coates 2007). Similarly,

coyotes have been able to spread farther beyond their prehistoric ranges in the United

States (and thus become domestically “invasive”) because of their ability to find food and

reproduce in areas of high human habitation. This underscores one of the main points of

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our research approach: that species introductions cannot be understood in isolation from

the human component (also see Cadotte 2009a).

Figure 1. Location of iguana sightings at the Condado Lagoon (top left), Torrecilla Lagoon (top right), San José Lagoon(bottom left), and Caño Martín Peña (bottom right).

Figure 2. Ordinal Logistic Regression model estimating the probability of encountering a green iguana as a function of distance to a non-mangrove vegetation edge (left panel) and

distance to a human settlement edge (right panel). Analyses were made using JMP 7.0 (SAS Institute).

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B. Variation in cultural experiences, attitudes and values about green iguanas in Puerto Rico

We conducted interviews with residents, recreational and subsistence resource users

of the estuary to assess the following crucial management-related questions:

- What do people think about introduced species, particularly about the green iguana, in Puerto Rico?

- What do people know about the green iguana and how does their knowledge

compare with news/media accounts of iguana introductions and with ecological monitoring results?

- What effect, if any, have green iguanas had in the use and enjoyment of the SJBE

by residents and visitors?

Semi-Structured Interviews

We conducted 15 ethnographic, semi-structured interviews with SBJE residents

and 25 structured intercept interviews with SBJE recreational and subsistence resource

users.

The semi-structured interviews with residents and people with continued

experience on the estuary consisted of extended conversations about green iguanas and

exotic species in the SJBE and, using an interview guide or protocol that included basic

demographic data and questions about the respondents’ experiences with green iguanas in

the estuary. Answers were recorded by taking field notes during and immediately after

the interviews. Field notes were entered into word processing software and analyzed for

content and recurrence of topics and themes using Atlas.ti (Muhr 2004) qualitative

analysis software.

Respondents to the semi-structured interviews included SBJE residents (10),

Gardeners/groundskeepers (3) and crabbers/fishermen (2). Nine were male and 6 were

20

female. All respondents reported continued experiences with iguanas in the estuary and

expressed interest in collaborating with SJBE officials and researchers to learn and

exchange information about the green iguana. They reported that there have been iguanas

in the SJBE for at least 20-30 years, especially towards the eastern portions of the

estuary. All reported that at present they know that iguanas were introduced to Puerto

Rico by pet shops and the pet trade before they escaped and became established in the

wild. However, six informants reported not realizing that the iguanas were introduced or

non-native until recently (about the last 5 years), with the increased coverage of iguana

introductions in the news media.

Seven of the interviewed residents had an overall positive attitude towards

iguanas, saying that they were an interesting part of the landscape that they and/or their

families enjoyed watching and interacting with. Six informants reported mixed feelings,

citing that while they sometimes enjoyed watching iguanas, they were sometimes

inconvenienced by iguanas near their homes or that they were worried about the iguanas’

effects on the ecosystem. The three main sources of iguana-caused inconveniences cited

by respondents were related to iguanas feeding on or otherwise damaging residential

gardens, iguana-car collisions or near-collisions in roadways, and iguanas causing fear or

disgust to residents due to the iguana’s physical appearance. Two informants expressed

that they did not welcome the iguanas in the SBJE landscape (or in Puerto Rico, for that

matter) at all.

All informants showed interest in learning more about the iguanas. Specifically,

12 of them wanted to know more about studies of what the iguanas are doing and how

they affect the environment locally, in the SJBE and in Puerto Rico. For example, several

21

informants (10) expressed confusion about media accounts of the iguana as a predator of

native bird eggs and amphibians because their own personal observations indicated that

iguanas were vegetarian creatures. They also expressed that they would like to see a

serious study about iguana diets. Due to their interest in knowing more about the green

iguana, the informants reported that they actively seek information about iguanas, iguana

behavior, effects of iguanas in the ecosystem and their potential to harm people and pets.

Their main sources of information about iguanas were personal observation,

conversations with friends, neighbors, and acquaintances, library books, and the internet.

Most of the interviewed SBJE residents (12) found the idea of systematically

killing green iguanas as a control strategy objectionable, citing the iguanas “right to live”,

the fundamental tenet of “respect for life”, and that “they are also creatures of God”.

Also, several informants mentioned that they would feel bad if iguanas were

systematically slaughtered because “the iguanas did not ask to be here”. The following

excerpt from a June 2008 interview with a 64 year old security guard illustrates this:

R: “I feel very sorry when I see an iguana “esparrachá” (as road kill) en la carretera. They are beautiful little animals!”

CGG: What do you think about killing iguanas as an introduced species control strategy? R: “I don’t like it. I do not understand why (people would do this). The iguanas did not ask to be here, to be brought here to Puerto Rico. Whoever kills a little animal just like that, forgets that up there, there is a God watching us.”

However, several informants considered two exceptions where it would be

acceptable to kill iguanas: 1) When their presence becomes a grave physical hazard for

humans (e.g. when basking iguanas interfere with airport safety in airport runways), and

2) if the iguanas are being slaughtered as a food resource. A quote from male informant

22

who is a municipal employee and a part-time small-scale farmer illustrates this: “Many

people, in Puerto Rico, are poor, they do not have money to go to the supermarket and

buy good quality meat. Many of you in San Juan don’t see it, but there is hunger in

Puerto Rico. The iguana is a good food resource, and people should use it”( interview,

May 2008). However, this same informant mentioned that he would not like to see a for-

profit industry of iguana meat products in Puerto Rico. He was especially opposed to the

idea of iguana meat becoming a luxury food item. This is because, in his words, iguana

meat “would become an expensive foodstuff, which would exclude people who do not

have the money, just like it happens nowadays with meat in the supermarkets”.

Structured intercept interviews with SBJE recreational and subsistence resource users

A short, structured questionnaire was administered to 25 recreational resource

users of the SJBE. Questionnaire respondents were intercepted while the respondents

were visiting the estuary recreational facilities in the Parque Central and Piñones of the

SJBE (see figure 1) areas on haphazardly chosen dates (usually the same day field iguana

census observations were carried out). The structured questionnaire was designed and

pre-tested for a 15-20 minute interview, and consisted of short, focused questions about:

1) respondents’ intended activities in the SJBE, 2) attitudes and knowledge about

introduced species in general and about the green iguana in Puerto Rico and the SJBE, 3)

their experience with iguanas in the SJBE, and 4) the effects that green iguanas have in

their use and enjoyment of the estuary. Besides this information, we also collected basic

demographic data to test whether factors such as education, gender, or place of residence

had an effect on the responses. Answers to questionnaire items were recorded by the PI

23

and research assistants in the field by filling out a structured interview instrument and

later coded for analysis.

The respondents to the structured questionnaire were residents of 9 municipalities

of Puerto Rico (San Juan, Dorado, Trujillo Alto, Caguas, Carolina, Loíza, Bayamón,

Caguas, and Toa Baja). 22 were visiting the SJBE for exercise/leisure activities and 3

were engaging in subsistence/recreational fishing and land crab hunting. Their ages

ranged from 18 to 60 years old (average 38 years old). Their self-reported highest

completed education levels included: High School (8), College (13), and Graduate

Degrees (4). Thirteen respondents were female and 12 were males.

Attitudes towards exotic species and the green iguana

Several intercept interview respondents (16) expressed confusion about what the

terms “exotic species” or “introduced species” meant. It was often necessary to further

explain the concept to respondents (e.g. species introduced by people to localities where

they did not occur otherwise and which became established in the wild).

Questionnaire items asking people’s opinions of exotic species and about green

iguanas in Puerto Rico were coded by whether they represented: 1) positive, 2) negative,

or 3) neutral/ambiguous opinions and/or attitudes about these matters. There was ample

variation in the respondent’s general opinions about exotic species in PR (6 positive, 8

negative, 11 neutral/ambiguous). Opinions about the green iguana in Puerto Rico were

slightly more positive (12 positive, 7 negative, 6 neutral/ambiguous).

24

We tested whether there were relationship between demographic characteristics of

the respondents such as (highest education level completed, gender, age) and their

attitudes towards exotic species and iguanas. We found no significant relationships in the

comparison, except for a weak relationship between highest education completed and

attitudes towards exotic species in general (X2= 8.736; p=.068), that indicates that people

with higher education levels tended to have more formed opinions towards exotic

species, and thus less neutral/ambiguous responses, than people with lower completed

education levels (there were almost equal numbers of positive vs. negative responses).

This might suggest that those with college-level education have been introduced more

often to scientific and news media about the global concern for species introductions.

However, since we identified ourselves as university researchers, this response pattern

might also just mean that college educated respondents were more confident in telling us

their opinions than non college-educated respondents. A larger sample with more

respondents would probably be needed to differentiate between these two possibilities.

Table 1. Relationships between some demographic parameters and intercept questionnaire respondents’ attitudes towards exotic species and the green iguana in Puerto Rico

Attitude towards Exotic Species Attitude towards Green Iguanas

Chi sq. p Chi sq. p

Age 1.11 0.57 2.3 0.32

Gender 0.05 0.97 1.12 0.57

Ed. Level 8.74 0.07 3.44 0.49

25

The textual responses provided by the respondents to the questionnaire reveal

perhaps more tellingly the variation in people’s opinions about iguanas. Answers to the

questions about the presence of iguanas in Puerto Rico’s estuaries ranged from “I love

them (the iguanas). I enjoy watching them immensely” (September interview with 30 year

old female), and “They do not bother me. The iguanas do not affect me one way or the

other” (August 2008 interview with 35 year-old male) to “I hate those animals, they are

ugly and we should kill them all” (July 2008 interview with 59 year old male).

C. What do green iguanas eat? Local and scientific knowledge in the controversy about the green iguana introduction

The diet of the iguana, specifically whether green iguanas routinely eat animals

such as birds, small eggs, lizards (Anolis sp.), coquí tree frogs (Eleutherodactylus sp.),

and insects, is at the heart of the controversy in media and scientific circles regarding the

introduction of the green iguana and the possible impact of the green iguana in Puerto

Rico. Although the vast majority of the scientific literature indicates that green iguanas

are herbivores, news media coverage of iguana introductions tends to emphasize the

largely unsubstantiated accounts that iguanas in the wild will pursue and eat small native

fauna (e.g. Cedeño and Cordero 2009).

Along with our team’s field observations of iguana feeding behavior and diets, we

wanted to know what SJBE residents and resource users think green iguanas eat. We

asked 28 of SJBE residents and resource users to freelist all the items that to their

knowledge are eaten by iguanas. The freelisting elicitation technique is used to elicit the

items comprising a cultural domain (Bernard 2002; D’Andrade 1995). We used

ANTHROPAC X (Borgatti 2001) to analyze the freelists for frequency of appearance in

26

lists, average rank, and Smith’s S salience (a composite parameter from frequency and

average rank of an item across all the lists in the sample) (Borgatti 1996). Smith’s S was

used as the principal criterion for ranking iguana diet items listed by the 28 respondents

to the freelist exercise.

Table 2 shows the total number of items mentioned by respondents as being part

of green iguana diets, along with frequencies and Smith’s salience values. A relatively

small number repeated items form the bulk of the responses, a j-curved pattern of

“consensus within diversity” (Barrett 1995) that indicates that there is consensus among

respondents about core domain items (figure 3). The most salient and frequently

mentioned core iguana diet domain items mentioned by SJBE residents and resource

users were all plant materials, with the first 10 items in terms of salience and the first 11

in terms of frequency being plants. Of the total 76 cumulative items mentioned in all the

lists of iguana diets, 62 were plant material, 9 were animal material, and 5 were non-

specific in terms of plant/animal material (e.g. leftovers, “whatever it finds”, etc.).

The residents’ responses are more similar to our systematic field monitoring and

experiment results than the supposedly science-informed media. Our ecological

monitoring activities, which have included focal observations of iguanas, bird nest

predation experiments, and iguana stomach content analysis, indicate that green iguanas

in the SJBE are feeding as strict herbivores (Carlo and García-Quijano 2009). Together

with qualitative interview data, these results suggest that the respondents pay more

attention to their own observations of, knowledge about, and experience with green

iguanas than to media accounts that tend to emphasize fears about the iguanas as

predators of native fauna. This underscores residents and resource users’ potential as

27

possible collaborators to managers in monitoring iguanas and other introduced species

activities in the ecosystem (also see Bart 2009).

Table 2. Items mentioned by SJBE residents and resource users in freelisting exercises about items eaten by the green iguana.

Freelist Item Smith's S FREQUENCY Leaves 0.268 9 Plants 0.182 7

Vegetation 0.179 5 Lettuce 0.158 6

Hibiscus flowers 0.095 3 Fruit 0.092 5

Grass 0.076 4 Flowers 0.057 2

Vegetables 0.054 2 Food scraps 0.051 4

Meat 0.049 2 Insects 0.042 2 Bread 0.036 1

Mosquitoes 0.036 1 Whatever it finds 0.036 1

Mangroves 0.036 1 Citrics 0.036 1 Trees 0.036 1

Bananas 0.036 1 Anolis Lizards 0.031 1

“Moca” tree 0.031 1 Red Currant 0.027 1

Guavas 0.025 2 Peanut flower 0.024 1

Cabbage 0.022 1 Mangos 0.018 1

Sweet potatoes 0.018 1 Bread 0.018 1

Carrots 0.018 1 Eggs 0.018 1

Apples 0.013 1 Carrion 0.012 1

Pears 0.009 1 Skink lizards 0.009 1

Oranges 0.009 1 “Húcar” trees 0.004 1

28

Figure 3. Graph showing salience (Smith’s S) of items mentioned in iguana food freelist exercises.

0

0.05

0.1

0.15

0.2

0.25

0.3

HOJAS

PLANTAS

VEGETACION

LECHUGA

AMAPOLAS

FRUTAS

HIERBA

FLORES

VEGETALES

SOBRAS

CARNE

INSECTOS PA

N

MOSQUITOS

LO QUE ENCUENTRA

MANGLES

CITRICOS

ARBOLES

GUINEO

LAGARTIJOS

MOCA

ACEROLA

GUAYABA

FLOR DE MANI

REPOLLO

MANGO

MALANGA

GALLETAS

ZANAHORIA

HUEVOS

MANZANA

ANIMALES MUERTOS

PERA

CIGUANAS

NARANJA

HUCAR

Mentioned iguana diet items

Smith's S

D. Interactions between green iguanas and Puerto Rico’s tourism industry

A repeated theme in our ethnographic interviews about the green iguana in Puerto

Rico was that green iguanas were becoming animals of interest for foreign and local

tourists visiting coastal, estuarine and riverside areas in San Juan and eastern Puerto Rico.

This supported our own observations of tourism industry’s use of iguanas (large,

interesting, and prehistoric-looking land animals which are easily observable and can be

tamed) as an attraction and entertainment for tourists.

Probably the most well-known use of iguanas as entertainment for tourism in

Puerto Rico is the “iguana-feeding stations” and “iguana watching/iguana crossing” signs

that have been posted for more than 5 years by the Westin Riomar Resort in Río Grande,

Puerto Rico (Figure 2). Our ethnographic informants also mentioned the proliferation of

iguana-watching kayak and boat tours in the SJBE, as well as other coastal Puerto Rican

29

locations, caged iguanas kept in the lobbies and pool areas of luxury hotels in (the same

way that other exotic-looking animals such as flamingos, parrots, peacocks, monkeys,

and toucans have kept in Puerto Rico hotel common areas for decades), as well as

repeated instances of both Puerto Rican and foreign tourists asking SJBE residents for

good iguana-watching spots. In virtually all of our field visits to the Parque Lineal area of

the SBJE we observed people (individuals, couples, and family groups) engaged in

watching iguanas and sharing observations about the iguanas.

Tourism is an important and growing source of revenue in coastal areas of

tropical islands, including Puerto Rico. One of the ways tourism generates revenue for

receiving locales is the selling of souvenirs, objects such as photographs, postcards,

clothing, figurines, and others, that serve as a remembrance of a salient or interesting

feature of the visited country or locales. The main purpose of buying a souvenir is to

acquire an object which can later serve as a symbol or a memory-generating object of the

visited locale, for either the visitor or a person back home who receives the item as a gift

(Goldman 2004)). Because of this, we hypothesized that if in fact green iguanas were

becoming important for Puerto Rico’s tourism industry, we should see significant

presence of iguanas as souvenirs in tourist gift-shops.

To test this hypothesis, we conducted a systematic cultural mapping exercise in

tourist gift-shops located in the tourism center of Old San Juan, Puerto Rico. The cultural

mapping exercise consisted of visiting all the tourist gift shops in Old San Juan and

systematically looking at the items on sale to look for green-iguana based or inspired

objects. We also interviewed gift shop clerks and/or owners to ask them about tourist

demand for iguana-theme items and, if iguana-themed items were found, why they had

30

made the decision to include these objects in their inventories. We also wanted to know

whether tourists would ever visit stores asking specifically for iguana memorabilia.

If an iguana-themed item on sale was found, we recorded the name and location

of the store, a description of the item, the selling price, the place of manufacture or

fabrication of the item, whether the item specifically referred to the green iguana, to

iguanas in Puerto Rico, and if the iguana figure or item had the iguanas appearing

together with the words “Puerto Rico” or with one or more established symbols of Puerto

Rico such as coquí tree frogs (Eleutherodactylus sp.), the Puerto Rican parrot (Amazona

vittata), the Puerto Rican flag, iconic musical cultural symbols such as the “cuatro”

guitar, and others.

The sampling universe consisted of 54 stores of varying sizes located through the

OSJ area but mostly concentrated in the Fortaleza and San Francisco Streets). We found

78 iguana-themed souvenir items in 33 of the 54 tourist gift shops. The items ranged from

cheap, mass-produced items such as postcards and trinkets (e.g. magnets, shot glasses,

plastic toys) selling for a few dollars to luxury items like hand-carved precious wood

statues prices selling for several hundred dollars. However, souvenir gift shop trade is

mostly a small-priced commodity trade; thus the median price of all the iguana-themed

items detected was $12.50. The iguana-themed items ranged from locally-made artisanal

items to mass-produced commodities made in places like Indonesia, Mexico, China,

Ecuador, and the USA.

The kinds of iguana-themed items we found in this cultural mapping exercise

included t-shirts, carvings, refrigerator magnets, dolls, figurines, rubber toys, shot

glasses, water-filled glass balls, puppets, post cards, beach towels, incense holders, flutes,

31

small tambourines, and others. Seventy-four of the items referred specifically to Iguana

iguana and 57 of those referred specifically to green iguanas in Puerto Rico. Fifty-four

items had green iguanas together with the words “Puerto Rico”. Finally, 19 items had

iguanas appearing together with other cultural symbols of Puerto Rico, such as cuatro

guitars, coquí frogs, “vejigante” carnival masks, and the Puerto Rican parrot. A second

round of cultural mapping exercise is currently underway, to verify whether iguana-

themed souvenir items are increasing over time or not, to perform additional observations

to estimate the proportion of iguana-themed items to other iconic Puerto Rican fauna.

The short informal interviews with gift shop store clerks and owners revealed that

foreign tourists routinely go into gift shops asking specifically for iguana-themed

souvenirs. Moreover, the gift shop store owners told us that they had increased the

number of iguana-themed items in their inventories mostly as a response to consumer

demand. That is, that the tourists’ own experiences and observations of green iguanas had

compelled them to look for iguana souvenirs when they visited gift shops. A gift shop

clerk described this process: “tourists see the iguanas in hotel lobbies or in the wild, or

the tour guides take them to see the iguanas. The tourists find them impressive and then

they come here and ask, specifically, about iguana things” (07/14/08 interview). This

may indicate that iguanas are a salient component of at least some foreign tourists’

experiences in the island. As one of the gift shop owners put it, “(the iguanas) are part of

the island, they are part of what you see in the island. And they are something impressive.

For the tourist, the iguana is like a coquí (frog)” (07/14/08 interview).

If we had any doubts about whether our souvenir shop cultural mapping exercise

was more than just a trivial observations, these doubts quickly dissapeared when the

32

initial technical report that included results of our tourism cultural mapping exercise were

made available to the Puerto Rican media through the SJBE research office. At least 4

articles quickly appeared in “El Nuevo Dia” and “Primera Hora”, two of the three

principal Puerto Rican newspaper, with headlines such as “La Iguana Verde Amenaza

Permanencia Del Coquí Como Imagen Turística” (The Green Iguana Threatens the

Importance of the Coquí as A Tourism Symbol) (Justicia Doll 2009; Cordero 2009).

Clearly, many Puerto Ricans hold in high regard the coquí frog as an international

symbol for Puerto Rico. Worries about green iguanas displacing coquí frogs in souvenir

shops are probably unwarranted, since more than 500 different coquí-themed souvenirs

were counted in our exercise, compared with 74 iguana-themed ones. However, the

reaction to the presence of the iguana in the tourist souvenir trade shows how even

symbolic interactions between native and exotic fauna (real coquí frogs are not affected

one way or another by iguana items in tourist shops) can be a significant cultural impact

for people in the host geographic location.

Figure 2. “Iguana crossing” and “Iguana feeding station” signs in the Westin

Riomar Resort in Río Grande, Puerto Rico.

33

Figure 4. Examples of iguana-themed tourist memorabilia sold in Old San Juan tourist gift shop stores.

34

Conclusion

Anthropogenic species introductions are, by definition, a human phenomena. As

such, they are driven by cultural, social, and technological factors as much as they are

driven by biological ones. However, with some important exceptions, social sciences and

specifically applied anthropology have been largely left out of the study of species

introductions. Despite worldwide alarm, the rate of species introductions seem to be only

accelerating and achieving a comprehensive, interdisciplinary understanding of the

phenomena is becoming only more urgent.

The results presented in this article were used for developing several

recommendations regarding the management of green iguanas in the SJBE. These

recommendations are detailed in the insert below.

Management Recommendations resulting from sociocultural component

of green iguana monitoring activities: 1. Further exploring the potential of people in the SJBE as plausible collaborators in the monitoring of green iguanas activities. 2. For as long as there are iguanas in the estuary, to take advantage of the green iguanas’ positive interactions with the tourism industry and charisma as an interesting species to organize activities that might channel revenue to SBJE mostly impoverished residents; as well as to promote people’s interest in the estuarine ecosystems of SJBE and their protection from urban development. 3. Because of the high spatial clumping of iguanas and their association with

In our opinion, the most potentially fruitful approach to their study of species

introductions and their impacts on host ecosystems (human and non-human alike) is to

recognize that species introductions are complex -and in many cases unavoidable-

phenomena, with varied interactions and outcomes. In an insightful conclusion to the

2008 review article on the cultural aspects of species introductions, Pfeiffer and Voeks

stated that “recognition of the biocultural dimensions of invasive biota can contribute to

35

a more balanced invasive species debate, whereby the function and meaning of invasive

plants and animals to (diverse human) communities is no longer absent from research,

management, or policy considerations”. We align ourselves with Pfeiffer and Voeks’

argument, perhaps adding that incorporating social and cultural dimensions of species

introductions will yield the best results within interdisciplinarily-conceived studies that

merge ecological and social sciences.

The results of our work with SJBE residents, resource users, an the San Juan

tourism industry resonate with previous findings elsewhere that people have varied

interactions, some positive, some negative and some neutral, with native and exotics

components of their ecosystem alike. Together with our findings about the spatial

association of introduced species and human activities, they also underscore that human-

dominated ecosystems and interactions within them are best understood when people are

conceptualized as part of the ecosystem and not some external factor to be addressed in

the policy and enforcement arenas only.

36

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