Introduction to Biodiversity ASAB – NUST Fall 2012

Introduction to Biodiversity

ASAB – NUSTFall 2012

The variety of life

is biological diversity.

Use of the term “biological diversity”in its current sense beganin 1980.

Biodiversity = biological diversity

Coined in 1985 for a conference, the proceedings of which were published as the book “Biodiversity”edited by E. O. Wilson.

What does it mean?

The variability among living organisms from all sources including terrestrial and aquaticsystems and the ecological complexes of which they are a part; diversity withinspecies, among species, and of ecosystems;interactions at all levels among organisms.

From Frankel et al., 1995, The conservation of plant biodiversity.

Fundamental levels of organization

•Genetic

•Organismal

•Ecological

Ecological Diversity

• Communities of species, their interactions

• Communities + resources (energy, nutrients, etc.) = ecosystem

• Measured primarily in terms of vegetation but relative abundance of species also important

• No unique definition and classification at the global level

Organismal Diversity

• Individuals, species• Mostly measured by numbers of

species• Estimated 1.7 million species

described to date• Estimated total number ranges

from 2 to 50 million (up to 100 million) species

• Mostly microorganisms and insects

Genetic diversity

• Heritable variation within and between populations of organisms

• Encoded in the sequence of 4 base-pairs

that make up DNA• Arises by mutations in genes and chromosomes• Very small fraction of genetic diversity is outwardly expressed

Why care about what we can’t see?

• Genetic variation enables evolutionary

change and artificial selection• Estimated 109 different genes across the Earth’s biota• Represents a largely untapped

genetic library

Ecosystems

Scale of relationships

Molecules smallestGenesCellsOrganisms (individuals)PopulationsSpeciesCommunitiesEcosystemsBiomesBiosphere largest

Ecological Principles

• Everything is connected to everything else.

• Everything has to go somewhere.

• There is no free lunch in nature. (Or, you don’t get something for nothing.)

Communities

Community: all of the organisms in a given area (habitat) and their interactions.

Ecosystems

Ecosystem =biotic community + abiotic environment

Nutrients suchas carbon, etc.

e.g., flower + pollinator

Energy from the sun

Precipitation, etc.

Ecosystems

to

The scale can be…

very small(a leaf)

very large(global)

Energy flow is one-way through ecosystems.

Materials (nutrients) are cycled through ecosystems.

Ecosystems

Ecosystems—1) Energy processes

Photosynthesis

Respiration


Photosynthesis transforms radiant (solar)energy into chemical energy (stored as chemical bonds in sugars and carbohydrates.

CO2

O2

sugars,starchesin cells

sun plant


Respiration is a step-by-step process thatallows organisms to use the energy stored the chemical bonds manufactured during photosynthesis.

sugars,starches

energy for cellular work+heat

O2

Ecosystems—2) energy users

There are three main categories of organisms according to the ecological roles they play:

1)Producers (primary producers, autotrophs)

2)Consumers (heterotrophs)

3) Decomposers (a special type of consumer)


Producers capture the sun’s energy and transform it into chemical energy through photosynthesis.

plants + algae + blue-green algae


Consumers are organisms that eat other organisms.Herbivores eat producers directly, carnivores eatother consumers.

Herbivores (grazers, primary consumers)

Examples: panda eating bamboo, bird eating nectar or flowers snail grazing on algae


Consumers are organisms that eat other organisms.Herbivores eat producers directly, carnivores eatother consumers.

Carnivores (secondary or tertiary consumers)

Examples: limpkin eating apple snails American alligator amoeba


Decomposers (detritivores) are a type of consumer that feed on dead organic matter—they can obtain this from any of the other trophic levels.

fungi and many bacteriabut also scavengers suchas vultures

Ecosystems—3) Energy flow

Energy flow is one-way through ecosystems.

WHY?


In any energy transformation (e.g., from one trophic level* to another) there is a net loss of usable energy.

*Trophic level: feeding relationships, who is eating whom.


Lost as heat

Lost as heat

sun plant cow jaguar

decomposer decomposerdecomposer


Lost as heat

1-5%

captured

10%

90%

10%

90%

10% 10% 10%

90% 90%90%

Lost as heat

sun plant cow jaguar

decomposer decomposer decomposer


Carnivores, especially secondary or tertiary ones, are rare.

carnivores

herbivores

producers

Ecosystems—Materials

Water and elements (e.g., carbon, nitrogen) and other materials are cycled through ecosystems.

They move between organic and inorganic phases by both biotic and abiotic processes.

The diversity of microorganisms (especiallybacteria) controls key steps in various cycles(see textbook examples of the nitrogen cycle,the carbon cycle, etc.)

Ecosystem Services

• Services provided by biodiversity that keep ecosystems functioning.

• Often thought of in terms of human wellbeing.

• Indirect-use value of biodiversity (these services are not factored into the marketplace).

Ecosystem Services—examples

• Photosynthesis

• Nutrient cycling

• Decomposition

Tree of Life III: Eukaryotes (Fungi and

Animals)

ASAB - NUSTFall 2012

TOL III: Fungi and Animals

• Fungi and animals probably share a common ancestor with choanoflagellates (collar-flagellates) based on genetic data

• Cell wall components and other complex biosynthetic pathways are similar between fungi and animals


fungi animalschoanoflagellates

single-celledprotistanancestor

TOL III: Fungi

• Primarily terrestrial• No motile cells except in

reproductive cells of chytrids• Chitin in cell walls• Unique features of chromosomes

and nuclear division• Dominant part of life cycle has

only one set of chromosomes per nucleus

TOL III: Fungi

• Most are filamentous, multicellular; a few are unicellular (chytrids, yeasts)

• Oldest fossils 450-500 million years ago

• About 70,000 species described; estimated to be up to 1.5 million

• 4 lineages: chytrids, zygomycetes, ascomycetes, basidiomycetes

TOL III: Fungi

chytrids zygos ascos basidios

TOL III: Fungi

• Consumers by absorption• In addition to natural sources of

organic matter, can obtain nutrition from a wide variety of man-made substrates (cloth, paint, leather, waxes, jet fuel, photographic film, etc.)

• Food-obtaining strategies: decomposers, parasitic, predaceous, symbiotic

TOL III: Fungi

1) Decomposers: use dead organic matter through excretion of digestive enzymes

2) Parasitic: obtain organic matter from living cells; many cause disease this way (pathogens)

3) Predaceous: trap and kill small organisms (nematodes, protozoans)

4) Symbiotic: form mutualistic relationships with other organisms (lichens, mycorrhizae)

TOL III: Fungi

Structure, Growth and Reproduction

-usually consist of hyphae (thread-like filaments)-mass of hyphae = mycelium-grow under a wide range of conditions-reproduction mostly sexual by spores; but asexual reproduction is common

TOL III: Fungi

fungal mycelium on wood

TOL III: Fungal Diversity (chytrids)

• Mostly aquatic• Reproductive cells with a

characteristic flagellum• Unicellular or multicellular with a

mycelium• About 750 species• One cause of frog die-offs

TOL III: Fungal Diversity (zygomycetes)

• Mostly decomposers, a few parasitic

• Multicellular, filamentous• About 600 species known• Best known as the bread molds• About 100 species form

mycorrhizae with plant roots (now thought to include many more undescribed species)

TOL III: Fungal Diversity (ascomycetes)

• Filamentous except for yeasts (unicellular)

• Mostly decomposers or parasitic, some predaceous or symbiotic

• Over 30,000 described• Includes most Fungi Imperfecti (e.g.,

penicillium)• Economic importance: yeasts (bread,

beer, wine); Dutch elm disease, chestnut blight, ergots; edible fungi (truffles, morels); antibiotics

TOL III: Fungal Diversity

ascomycetes

Cordyceps

scarlet cups

ergot on rye

TOL III: Fungal diversity

yeast (ascomycete)

breadwinebeer

TOL III: Fungal Diversity

edible ascomycetes

morels

truffles

TOL III: Fungal Diversity (basidiomycetes)

• Mainly decomposers and pathogens• About 25,000 species described• Ca. 5,000 species involved in

mycorrhizal associations• Economic importance: edible

(mushrooms, corn smut); poisonous; pathogens (rusts, smuts); decomposers (woodrotters)

TOL III: Fungal Symbionts

• Lichen = symbiosis with a green alga or blue-green alga (cyanobacteria)

• Fungal partner usually an ascomycete, usually about 90% of the lichen biomass

• Have a unique biology• Close to 17,000 species

TOL III: Fungal Symbionts

• Mycorrhiza = symbiosis between a fungus and a plant root

• Important in evolution of plants and fungi; allowed exploitation of many more habitats for both partners

• At least 85% of plants form mycorrhizae

• Involves zygomycetes (endomycorrhizae) and basidiomycetes (ectomycorrhizae)

TOL III: Mycorrhizal diversity

endomycorrhizae(zygomycetes)

ectomycorrhizae(basidiomycetes)


fungi animalschoanoflagellates

single-celledprotistanancestor

Tempeh and tofu

Tofu is made by coagulating soy milk and pressing the resulting curds. Although pre-made soy milk may be used, most tofu producers begin by making their own soy milk, which is produced by soaking, grinding, boiling and straining dried (or, less commonly, fresh) soybeans.

Tempeh is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form, similar to a very firm vegetarian burger patty

http://en.wikipedia.org/wiki/Soy_milk

http://en.wikipedia.org/wiki/Soybeans

http://en.wikipedia.org/wiki/Fermentation_(food)

http://en.wikipedia.org/wiki/Soybean

Characteristics features

The original Animal Kingdom proposed by Linnaeus included the protozoans, sponges, jelly fishes, worms, crabs, insects, spiders, snails, starfishes, sharks, bony fishes, frogs, lizards, birds and mammals. In general, animals exhibit the following distinguishing characters.•The animal body generally exhibits a definite symmetry, form and shape.•Animals have the capacity to move from place to place in search of their necessities.•Growth in animals is determined and occurs proportionately in all parts of the body.•Animals are generally heterotrophic, obtaining their food from plants and other animals.•Animals have the property of irritability - the capacity to respond to a stimulus.•The cells, which form an animal's body do not have a cell wall. •Plastids and vacuoles are generally absent and centrioles & lysosomes are present..•Animal cells cannot synthesize all the necessary amino acids, vitamins and coenzymes and as such will have to obtain them from external sources.•Reserve food is glycogen.

TOL III: Animals (Metazoa)

• Multicellular consumers by ingestion

• Storage product is animal starch (glycogen)

• Most have nervous tissue and muscle tissue (which are unique to animals)

• Most are mobile

TOL III: Animals

• Gas exchange through aqueous medium surrounding the organism or through specialized gas exchange structures (e.g., gills or lungs)

• Some kind of internal circulation system present (food, gases, maintenance of proper water and mineral concentrations, waste elimination)

TOL III: Animals

• Animals arose in the oceans from single-celled protistan ancestors

• The earliest animals appeared at least 1 billion years ago

• Most modern groups of animals appeared around 600 million years ago (the Cambrian explosion) in the oceans

TOL III: Animals

• About 35 major modern lineages (phyla) and several fossil lineages of animals are known

• In contrast, protists have at least 16 major lineages, plants have 12 modern and 5 fossil lineages, and fungi have 4 modern lineages

• Over 1 million species of animals are known; >75% of these are insects

TOL III: Animals

• Of the 35 modern lineages of animals, most remain aquatic (marine)

• About half of the lineages are exclusively marine

• Only 5 lineages have adapted to land (nematodes, annelids, mollusks, arthropods and chordates represented by vertebrates)

• Only the nematodes, arthropods and vertebrates have diversified extensively on land

64

Fig. 1a. Phylogenetic Tree for Major Phyla of Animal Kingdom

65

Fig.1b. Changes in body plan added (-------)

9 Phyla of the Animal 9 Phyla of the Animal kingdomkingdom

1)Porifera 6) Mollusca

2)Coelenterata 7) Echinoderm

3)Flatworms 8) Arthropoda

4)Roundworms 9) Chordata

5)Segmented worms

sponges radiates

annelidsmollusks& others

arthropodsnematodes& others

chordatesechinoderms

simplifiedevolutionary treefor the animal kingdom

TOL III: Animals (major lineages)

• Earliest lineage of animals is the sponges

• Least specialized of all animals• Lack any kind of tissues• Tissue = an integrated group of

cells with a common structure and function (e.g., muscles, nerves)

sponges radiates




presence of tissues


• The next major adaptation, after the evolution of tissues, was the split between radial vs. bilateral body symmetry

• Radial = parts radiate from the center, any plane through the animal creates two equal halves

• Bilateral = has two sides, left and right, such that a plane through the animal can be placed only one way to get two equal halves

TOL III: Animals (radiates)

• Radial symmetry an adaptation to a more sedentary lifestyle in which the organism stays in one place and meets the environment equally from all sides

• Radiates (or cnidarians) have stinging tentacles

• Include the jellyfish, sea anemones, and corals

sponges radiates




presence of tissues

bilateral symmetry


• Bilateral symmetry is an adaptation to a more active lifestyle in which the organism moves around to obtain food and must detect and respond to stimuli

• Associated with the concentration of sensory function into the head

• The three major groups of bilateral animals exhibit various specializations in the formation of the body cavity

TOL III: Animals (annelids & friends)

banana slug (mollusks)

earthworms (annelids)

leeches on a turtle

Phylum Mollusca(mollusks)*

• Second largest animal phylum

• 93,000 living species (35,000 fossil species)

• Mostly are marine, some freshwater and terrestrial

• Incredible morphological diversity

*Material thanks to Dr. Jeanne Serb

Class Gastropodasnails, slugs, sea slugs

Class Cephalopoda squids, octopus, cuttlefish, nautilus

Adaptations to predatory life style

• Active and very mobile – Closed circulatory

systems

• Camouflage– Chromatophores in skin– http://www.youtube.com/watch

?v=SCgtYWUybIE

• Exceptional vision

• Beak to tear prey

• Arms (tentacles) to grip prey

http://www.youtube.com/watch?v=SCgtYWUybIE

http://www.youtube.com/watch?v=SCgtYWUybIE

Class Bivalviaclams, cockles, mussels, oysters,

scallops

TOL III: Animals (arthropods & friends)

TOL: Arthropods (current diversity)*

regardless of how one measures diversity, the arthropods are among the most successful lineages

nearly a million described, w/ estimates of undescribed species reaching 40 million

have colonized all major habitats on earth: nearly all marine, freshwater, and terrestrial habitats

*material thanks to Dr. Greg Courtney

TOL: Arthropods Platnick (1992): “Speaking of biodiversity is essentially

equivalent to speaking about arthropods. In terms of numbers of species, other animal and plant groups are just a gloss on the arthropod scheme.”

Wilson (1999): “Entomologists often are asked whether insects will take over if the human race extinguishes itself. This is an example of a wrong question inviting and irrelevant answer: insects have already taken over… Today about a billion billion insects are alive at any given time… Their species, most of which lack a scientific name, number in to the millions… The human race is a newcomer dwelling among the masses… with a tenuous grip on the planet. Insects can thrive without us, but we and most other land organisms would perish without them.”

Arthropoda:Makes up 75% of the animal kingdomBasic Characteristics:

hard external skeletonsegmented bodyjointed legs

Ex: beetle, milli & centipede, spider, crab

TOL: Arthropods (major groups)

• 1)1) Chelicerates – includes Chelicerates – includes spiders, mites, scorpionsspiders, mites, scorpions

• 2)2) Crustaceans – includes crabs, Crustaceans – includes crabs, shrimp, copepods, barnacles, etc.shrimp, copepods, barnacles, etc.

• 3)3) Uniramia – includes Uniramia – includes millipedes, centipedes, insectsmillipedes, centipedes, insects

• 4) Trilobites – extinct, known only 4) Trilobites – extinct, known only from fossilsfrom fossils

TOL: Arthropods (major features)

• 1)1) Body segmented internally and Body segmented internally and externallyexternally

• 2)2) Tagmosis (regional body Tagmosis (regional body specialization of groups of specialization of groups of segments: e.g., head, thorax, segments: e.g., head, thorax, abdomen)abdomen)

• 3)3) Chitinous exoskeleton (with thin Chitinous exoskeleton (with thin areas between segments)areas between segments)

• 4)4) Segmented (jointed) appendagesSegmented (jointed) appendages• 5) Cephalization well developed5) Cephalization well developed

1)1) Small sizeSmall size

AdvantagesAdvantages::

a) assists escape, movement in confined a) assists escape, movement in confined

spacesspaces

b) need smaller bits of resourcesb) need smaller bits of resources

DisadvantagesDisadvantages::

a) small surface : volume ratio, which a) small surface : volume ratio, which

leads to leads to

increased heat and water lossincreased heat and water loss

Reasons for successReasons for success

ArthropodArthropodss

2)2) ExoskeletonExoskeleton


a) protection - much stronger than internal skeletona) protection - much stronger than internal skeleton

b) greater surface area for muscle attachmentb) greater surface area for muscle attachment

c) helps prevent desiccationc) helps prevent desiccation


a) constrained movementa) constrained movement

b) problems re. growth… needs to be shedb) problems re. growth… needs to be shed

c) respiratory, sensory, & excretory issues c) respiratory, sensory, & excretory issues

(impervious layer)(impervious layer)



Reasons for successReasons for successArthropoArthropodsds

3)3) Arthropodization (presence of jointed appendages)Arthropodization (presence of jointed appendages)Includes legs, antennae, mouthparts, etc.Includes legs, antennae, mouthparts, etc.

Permits fine-tuned movements, manipulation of Permits fine-tuned movements, manipulation of

food & other objects, locomotion, etc.food & other objects, locomotion, etc.

Regional specialization of body (tagmosis); e.g., Regional specialization of body (tagmosis); e.g.,

insect w/insect w/

(a) head: feeding, nerve & sensory center (a) head: feeding, nerve & sensory center

(b) thorax: locomotory center… legs, (b) thorax: locomotory center… legs,

sometimes sometimes

wingwing

(c) abdomen: specialized for reproduction & (c) abdomen: specialized for reproduction &

contains much of digestive systemcontains much of digestive system

4)4) Short life cycles - allows use of food resources Short life cycles - allows use of food resources

that may be available for only short period of that may be available for only short period of

timetime

5)5) High fecundity - typically several hundred to High fecundity - typically several hundred to

several thousand eggs (but is high mortality)several thousand eggs (but is high mortality)



6)6) Wings (re. most insects)Wings (re. most insects)


a) allow dispersal to food resourcesa) allow dispersal to food resources

b) increased potential for finding matesb) increased potential for finding mates

c) assist escape from predatorsc) assist escape from predators

d) miscellaneous: sexual displays, signalingd) miscellaneous: sexual displays, signaling


a) require lots of energy to producea) require lots of energy to produce

b) can be awkward / bulkyb) can be awkward / bulky

c) windy, exposed habitats?c) windy, exposed habitats?

Arthropods: InsectsArthropods: InsectsReasons for successReasons for success

7)7) MetamorphosisMetamorphosis


a) different life stages adapted for different habitats a) different life stages adapted for different habitats

& food& food

… … immature stages adapted for feeding & growthimmature stages adapted for feeding & growth

… … adults adapted for reproduction & dispersaladults adapted for reproduction & dispersal

b) minimizes competition between various life stagesb) minimizes competition between various life stages


a) require lots of energy for drastic changesa) require lots of energy for drastic changes

b) molting difficult, potentially damaging / dangerousb) molting difficult, potentially damaging / dangerous

Arthropods: InsectsArthropods: InsectsReasons for successReasons for success

sponges radiates




presence of tissues

bilateral symmetry

body cavitylining from thedigestive tube

TOL III: Animals (chordates and echinoderms)

echinoderms chordates

reversion to radial symmetry

body cavity lining from the digestive tube

dorsal nerve chord

TOL III: Animals (echinoderms)

starfish

sea urchins

TOL III: Animals (chordates)

• Chordates include all animals with a dorsal nerve cord

• About 50,000 species total– Tunicates– Hagfishes– Amphioxus– Vertebrates:

fishes, amphibians, reptiles, birds and dinosaurs, mammals

TOL III: Animals (chordates)

tunicates or sea squirts

TOL III: Animals (vertebrates)

fishes

birds and dinosaurs

reptiles and amphibians

mammals

TOL: Summary

1) Close to 2 million species of organisms have been described.

2) Estimates of total diversity range from 10 to 50 (in one case, up to 100) million species (with very conservative estimates as low as 5 million)

3) Species diversity in several groups, primarily micoorganisms, is grossly understudied and underestimated; among multicellular eukaryotes, fungi and nematodes are also relatively unknown

TOL: Summary

4) Prokaryotes ruled the world long before eukaryotes evolved; prokaryotes exhibit a wide array of metabolic diversity and so control key steps in many nutrient cycles.

5) Evolutionary trees of major groups provide frameworks for understanding the evolutionary history and major adaptive changes in those groups.

TOL: Summary

6) The ecological function of diversity can be subdivided by roles:a) primary producers: some bacteria (e.g., cyanobacteria; aquatic), some archaens (aquatic), algae (aquatic), plants (aquatic and terrestrial)b) consumers: some bacteria and archeans, protozoans, fungi, animals; includes pathogens and predators

TOL: Summary

6) cont’d.c) decomposers: primarily bacteria and fungi, also some fungus-like protists, as well as some animals such as nematodes; a few vertebrate carrion-eaters could also be considered as decomposersd) nutrient cyclers: many bacteria

TOL: Summary

6) cont’d.e) symbionts: diverse, many kinds of organisms are involved; includes mycorrhizae (plant root + fungus), endosymbionts (e.g., corals, dinoflagellates), lichens (cyanobacteria or green alga + fungus)

Arthropods rule!

Value and Maintenance of Biodiversity

ASAB – NUSTFall 2012

Value and Maintenance

• Benefits to humans, direct or indirect

• Intrinsic value• What kind of a world do we want

to live in?• Redundancy in ecosystems (how

much is enough?)

Benefits to humans

• Direct use value = marketable commodities– Food– Medicine– Raw materials– Recreational harvesting– Ecotourism

Benefits to humans: food

• About 3,000 species (ca. 1% of 300,000 total) of flowering plants have been used for food

• About 200 species have been domesticated

• Wild relatives source of genes for crop improvement in both plants and animals

Benefits to humans: medicine

• Organisms as chemists• About 25% of all medical

prescriptions in the U.S. are based on plant or microbial products or on derivatives or on synthetic versions

• Some medicinal products from animals (e.g., anticoagulant from leeches)

Benefits to humans: raw materials

• Industrial materials:– Timber– Fibers– Resins, gums– Perfumes – Adhesives– Dyes– Oils, waxes, rubber– Agricultural chemicals

Benefits to humans: recreational harvesting

• Recreational harvesting:– Hunting– Fishing– Pets– Ornamental plants

Benefits to humans: ecotourism

• By definition based on biodiversity

• Growing portion of the tourism industry

Indirect Use Value

• Indirect use value = services provided by biodiversity that are not normally given a market value (often regarded as free)

• Include primarily ecosystem services: atmospheric, climatic and hydrological regulation; photosynthesis; nutrient cycling; pollination; pest control; soil formation and maintenance, etc.

Indirect Use Value

• Biosphere 2 was an attempt to artificially create an ecosystem that would sustain human life

• Ca. US$200 million invested in design and construction plus millions more in operating costs

• Could not sustain 8 humans for two years

Intrinsic value

• Simply because it exists• Moral imperative to be good

stewards, the preservation of other life for its own sake

• Supported in many different religious or cultural traditions

• Recognized in the Convention on Biodiversity

Intrinsic Value

• Biophilia = the connection that human beings subconsciously seek with the rest of life (nature) or the innate connection of humans to biodiversity

Intrinsic Value


• Should we put a monetary value on everything?

Intrinsic Value


• Should we put a monetary value on everything?

• If something can be valued, it can be devalued.

What kind of a world do we want to live in?

•Human co-opt about 40% of the net primary productivity on an annual basis

•Human population at over 6 billion and growing at about 80 million per year

•Loss of some biodiversity is inevitable


• Current extinction rate much higher than background; also commitment to extinction

• Extinction is forever; species may have unforeseen uses or values (e.g., keystone species, medicinal value, etc.)

• Biodiversity has recovered after previous mass extinctions, but are we also eliminating that possibility by severely restricting conditions conducive to evolution?


If 6 billion people consume 40% of the annual net primary productivity, what is the theoretical limit (= carrying capacity) for humans under current conditions?

2.5 x 6 billion = 15 billion


But this number does not factor in the costs of dealing with wastes or non-renewable resources.

Nor does it leave room for other biodiversity, upon which we depend for ecosystem services (such as waste removal/recycling).

Human population is expected to reach ca. 12 billion by 2050.


• This is why many now argue that we have to find a way to put biodiversity into the economic equation

• Previously no monetary values were associated with natural resources except the actual ones generated by extraction (the world is there for us to use)


• Extraction costs (e.g., labor, energy) usually computed

• But cost of replacement not included, nor costs of the loss of the services provided by that resource or its ecosystem (e.g., cutting forest for timber)

• Because costs are undervalued, benefits of extraction are overvalued


• Green accounting proposed as part of the solution

• But requires that environmental assets have proper prices (p. 171, Chichilnisky essay in text)

• Tie in to property rights for natural resources

Redundancy in Ecosystems

•Or, how much biodiversity is enough?

•How much redundancy is built into ecological processes/communities?

•To what extent do patterns of diversity determine the behavior of ecological systems?


Two opposing views: rivet hypothesis vs. redundancy hypothesis

rivet redundancy


• Rivet hypothesis: most if not all species contribute to the integrity of the biosphere in some way

• Analogy to rivets in an aircraft—there is a limit to how many can be removed before the structure collapses

• Progressive loss of species steadily damages ecosystem function


• Redundancy hypothesis: species richness is irrelevant; only the biomass of primary producers, consumers and decomposers is important

• Life support systems of the planet and ecological processes will generally work fine with relatively few species


• In the past (from fossils), most ecological systems have been conspicuously less species rich

• But no evidence that they operated any differently


• Major patterns of energy flow and distribution of biomass in existing ecological systems may be broadly insensitive to species numbers

• But systems with higher diversity and more kinds of interactions may be more buffered from fluctuations

• Lack of data regarding the link between species-richness and ecosystem function


• Middle ground: ecosystem processes often but not always have considerable redundancy built into them– Not all species are equal (e.g.,

functional groups, keystone species)– The loss of some species is more

important than the loss of others– Species loss may be tolerated up to

some critical threshold

Documents

Introduction to Biodiversity ASAB – NUST Fall 2012