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Restoring aboveground carbon and biodiversity: acase study from the Nile basin, EthiopiaWolde Mekuriaa, Simon Langana, Robyn Johnstonb, Beyene Belayc, Dagninet Amarec,Tadesse Gashawc, Gizaw Destac, Andrew Nobleb & Abeyou Waled

a International Water Management Institute (IWMI), PO Box 5689, Addis Ababa, Ethiopiab International Water Management Institute (IWMI), 127 Sunil Mawatha, Pelawatte,Battaramulla, Colombo, Sri Lankac Amhara Regional Agricultural Research Institute, Bahir Dar, Ethiopiad Bahir Dar University, School of Civil and Water Resources Engineering, Bahir Dar,EthiopiaPublished online: 05 Mar 2015.

To cite this article: Wolde Mekuria, Simon Langan, Robyn Johnston, Beyene Belay, Dagninet Amare, Tadesse Gashaw,Gizaw Desta, Andrew Noble & Abeyou Wale (2015): Restoring aboveground carbon and biodiversity: a case study from theNile basin, Ethiopia, Forest Science and Technology, DOI: 10.1080/21580103.2014.966862

To link to this article: http://dx.doi.org/10.1080/21580103.2014.966862

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Restoring aboveground carbon and biodiversity: a case study from the Nile basin, Ethiopia

Wolde Mekuriaa*, Simon Langana, Robyn Johnstonb, Beyene Belayc, Dagninet Amarec, Tadesse Gashawc, Gizaw Destac,

Andrew Nobleb and Abeyou Waled

aInternational Water Management Institute (IWMI), PO Box 5689, Addis Ababa, Ethiopia; bInternational Water Management Institute(IWMI), 127 Sunil Mawatha, Pelawatte, Battaramulla, Colombo, Sri Lanka; cAmhara Regional Agricultural Research Institute, BahirDar, Ethiopia; dBahir Dar University, School of Civil and Water Resources Engineering, Bahir Dar, Ethiopia

(Received 1 April 2014; Accepted 19 August 2014)

In Ethiopia, exclosures in landscapes have become increasingly important to improving ecosystem services and reversingbiodiversity losses. The present study was conducted in Gomit watershed, northern Ethiopia, to: (i) investigate the changesin vegetation composition, diversity and aboveground biomass and carbon following the establishment of exclosures; and(ii) analyse the economic returns of aboveground carbon sequestration and assess the perception of local communities onland degradation and exclosures. A space-for-time substitution approach was used to detect the changes in abovegroundcarbon, species composition, and diversity. Exclosures of 1-, 2-, 3-, 4-, 5-, and 7-years-old and a communal grazing landwere selected. Household surveys, key informant interviews, and a financial analysis were used to assess the perception oflocal communities and the value of exclosure impacts, respectively. Significant (P D 0.049) differences in species diversityand considerable increases in aboveground carbon (ranged from 0.6 to 4.2 t C ha¡1), CO2 storage (varied between 2.1 and15.3 t CO2 ha¡1), woody species composition, and richness (ranged from five to 28) were observed following theestablishment of exclosures. Exclosures generated temporary certified emission reductions (tCER) of 3.4, 2.1, 7.5, 12.6,12.5, and 15.3 Mg CO2 ha

¡1 after 1, 2, 3, 4, 5, and 7 years, respectively. The net present value (NPV) of the abovegroundcarbon sequestered in exclosures ranged from US$6.6 to US$37.0 per hectare and increased with exclosure duration. At awatershed level, 51.4 Mg C ha¡1 can be sequestered, which represents 188.6 Mg CO2 ha

¡1, resulting in tCER of 139.4 MgCO2 ha¡1 and NPV of US$478.3 per hectare. This result would suggest that exclosures can potentially improve localcommunities’ livelihoods beyond rehabilitating degraded lands if carbon stored in exclosures is traded. Communities in thewatershed demonstrated that exclosures are effective in restoring degraded lands and they are benefiting from increasedfodder production and reduced impacts of soil erosion. However, the respondents are also concerned over the sustainabilityof exclosure land management, as further expansion of exclosures aggravates degradation of remaining communal grazinglands and causes fuel wood shortages. This suggests that the sustainability of exclosure land management can be attainedonly if these critical concerns are addressed by a joint effort among government agencies, nongovernmental organizations,and communities.

Keywords: aboveground carbon; carbon trading; ecosystems degradation; exclosures; plant species richness; plant diver-sity; tCER

Introduction

Human exploitation and the widespread loss of biodiver-

sity has resulted in a dramatic reduction in the provision-

ing of ecosystem services (MEA 2005; Chazdon 2008;

Guariguata and Balvanera 2009; Butchart et al. 2010;

Hector et al. 2011). In Ethiopia, land resources are facing

intense degradation as a consequence of deforestation,

agricultural land expansion, and overgrazing that results

in significant environmental degradation, loss of forest

biodiversity, and ecosystem services (Lemenih et al.

2005; Mengistu et al. 2005). For example, the rate of

deforestation in the Ethiopian highlands was estimated at

62,000 ha yr¡1 (World Bank 2001), average rate of soil

erosion for all land uses was estimated at 35 Mg ha¡1

yr¡1 (Keyser and Sonneveld 2001), and nutrient depletion

was reported as 30 kg ha¡1 of nitrogen and 15�20 kg

ha¡1 of phosphorus (UNDP 2002). Ecological restoration,

which aims to restore disturbed ecosystems, has been an

important approach to mitigate human pressures on

natural ecosystems (Holl et al. 2003) and improve ecosys-

tem services (Doren et al. 2009; Bullock et al. 2011), as

well as reversing biodiversity losses (Bullock et al. 2011).

Consequently, restoration of degraded watersheds through

establishing exclosures has become increasingly impor-

tant in Amhara regional state, in the northern highlands of

Ethiopia (Waesberghe and Mezemir 2010).

Exclosures are areas closed off or protected from inter-

ference from people and domestic animals, with the goal

of promoting natural regeneration of plants and reducing

land degradation of formerly degraded communal grazing

lands (Mekuria et al. 2011). The inception of exclosure

land management at a watershed level started in 2005

when 25 watersheds were selected and supported within

the framework of the Sustainable Utilization of Natural

Resources for Improved Food Security (SUN) program

(Waesberghe and Mezemir 2010). As part of the SUN pro-

gram, communities in the Gomit watershed established

exclosures on communal grazing lands in 2006. Priority

*Corresponding author. Email: w.bori@cgiar.org or wolde_mekuria@yahoo.com

ISSN 2158-0103 print/ISSN 2158-0715 online

� 2015 Korean Forest Society

http://dx.doi.org/10.1080/21580103.2014.966862

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areas for establishing exclosures were identified as a joint

initiative of local communities, a community watershed

team (CWT), government agencies, and nongovernmental

organizations (NGOs). The management and use of the

exclosures in the Gomit watershed is managed by CWT,

which represents the watershed community. The CWT is

actively involved in the planning and implementation of

the watershed development activities such as exclosure

establishment and protection, and construction of soil and

water conservation (SWC) structures.

Case studies conducted in the highlands of Ethiopia

have shown that exclosures can be effective in restoring

degraded ecosystems (e.g., Girmay et al. 2009; Yayneshet

et al. 2009; Mekuria and Veldkamp 2012; Mekuria 2013;

Yami et al. 2013) and in providing economic benefits

(Tilahun et al. 2007; Babulo et al. 2009; Mekuria et al.

2011). However, all of these studies have been conducted

in only two or three villages and so cannot adequately rep-

resent the diversity in soil, slope, exclosure management,

climate, and topography in the Ethiopian highlands. In

addition, the changes in aboveground biomass and carbon

and biodiversity following the establishment of exclosures

have not been inventoried systematically at a watershed or

landscape level. Although exclosures have been estab-

lished since 2006 in Gomit watershed, empirical data on

the effectiveness of these protected areas in improving

aboveground carbon, the economic returns of improved

aboveground carbon, and the impacts of exclosures on

livelihoods are lacking. Further, members of different cul-

tures or cultural groups may value forest biodiversity and

ecosystem services differently and, as a consequence,

may or may not support conservation goals set by gover-

nance bodies (Deng et al. 2006; Lindemann-Matthies

et al. 2014). There is a need to understand the perception

of local communities on the effectiveness of exclosures in

restoring degraded ecosystems and improving livelihoods.

A comprehensive study to investigate the biophysical

and socioeconomic changes following the establishment

of exclosures at a watershed level is critical for evaluation

of existing exclosures, designing ways of increasing

incomes of rural communities through exclosure estab-

lishment, and for deciding whether additional exclosures

should be established. Such understanding would help

maximize benefits for smallholders from existing exclo-

sures, which in turn will improve the livelihoods of the

local communities. The present study was conducted in

Gomit watershed, northern Ethiopia, to: (i) investigate the

changes in vegetation composition, diversity, and above-

ground carbon following the establishment of exclosures

on communal grazing lands over different time periods;

(ii) analyse the economic returns of sequestered above-

ground carbon; and (iii) assess the perception of local

communities on the effectiveness of exclosures in restor-

ing degraded landscapes and their contribution to improv-

ing the livelihoods of watershed communities. We

hypothesized that exclosures can be effective in restoring

degraded ecosystems, improving the livelihoods of water-

shed communities, and generating potential household

income through aboveground carbon sequestration.

Materials and method

Study area

The study was conducted in Gomit watershed located in

Libo Kemkem Wereda, South Gondar administrative

zone of Amhara region in northwestern Ethiopia

(Figure 1). Gomit watershed covers an area of 1483 ha

(Waesberghe and Mezemir 2010). The total beneficiary

population consists of 360 households. As in other parts

of the Amhara region, agriculture is the predominant sec-

tor of the economy in the Gomit watershed. The agricul-

tural sector is primarily dependent on smallholder

farming. The average farm size is 0.82 hectare per house-

hold. Smallholders cultivating fragmented microholdings

produce more than 95% of the annual agricultural output

(Waesberghe and Mezemir 2010).

The annual income of the very poor, poor, middle, and

better off communities in the Gomit watershed varies

between US$68 and US$89, US$121�132,

US$132�142, and US$168�195, respectively (USAID

2007). Our recent data from the household survey

reported here indicates that the average annual income of

the communities in the Gomit watershed is US$88.

Despite a long rainy season and moderately fertile clay

loam soils, the study site faces a food deficit every year.

Major problems that contribute to this food deficit include

population density, lack of income to buy agricultural

inputs such as fertilizers, and natural resource degradation

(USAID 2007; Waesberghe and Mezemir 2010).

In response to natural resource degradation problems,

the communities in the Gomit watershed are organized as

an association and started land rehabilitation efforts

through exclosure establishment and the construction of

soil water conservation (SWC) structures since 2006. The

association is given legal power over the use and manage-

ment of the natural resources. Accordingly, the Gomit

watershed association is formally registered under procla-

mation No. 1965 of 1960 of the civil code 1990. The

Gomit watershed association elected the CWT, which is

responsible for the management, protection, and use of

exclosures and other land rehabilitation efforts. The CWT

consists of nine members (seven men and two women).

Five of the nine members act as chair, deputy chair, secre-

tary, finance administration, and monitoring and evalua-

tion, while the remaining four are ordinary members.

To ensure the sustainable management of exclosures

and protection of the SWC structures, the Gomit watershed

association, together with CWT, drafted a bylaw based on

a model provided by the SUN program. The draft agree-

ment was presented to all watershed members for discus-

sion and approval. After discussion and approval from all

members, the draft agreement was legalized at zonal level,

which in turn enabled the communities to enforce their

bylaws and protect their resources from “free riders.”

In the Gomit watershed, the first exclosures were

established in 2006, and accordingly we selected 1-, 2-, 3-

4-, 5-, and 7-year-old exclosures as well as a communal

grazing land as a control treatment. We assumed that,

before establishment, exclosures and the communal

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grazing lands were in similar condition because the exclo-

sures were established on the same communal grazing

lands that were used for livestock grazing. The area of the

exclosures ranged from 2.4 to 14.0 ha while the commu-

nal grazing land covers an area of 3.6 ha (Table 1).

In exclosures, grass harvesting (using a cut and carry

system) is the only activity allowed, and is conducted

once a year. On the communal grazing land, unlimited

access for grazing is practiced. In exclosures, SWC struc-

tures such as hillside terraces, stone bunds, and microba-

sins have been constructed. The purpose of constructing

SWC structures in exclosures is to enhance biological

regeneration of degraded indigenous trees and shrubs, and

promote grass production through increasing the avail-

ability of water in the root zone.

According to the Ethiopian climate classification,

Gomit watershed has a woina dega tropical continental

climate.1 The mean annual rainfall (for the years

1992�2006) was 1148 mm yr¡1. The mean minimum

temperature was 11.8 �C, while the mean maximum tem-

perature was 27.0 �C. The altitude of the study sites range

from 1963 to 2056 m above sea level. The rainy season

usually occurs between June and September in which

87% of annual rainfall occurs (Figure 2). Major land uses

in the watershed include cultivated lands (23% of the

area), degraded secondary forest lands (53%), communal

grazing lands (18%), and other uses (6%). Mixed

crop�livestock farming is the backbone of household

livelihoods at the study sites.

Soils of the study sites were classified into three major

groups: chromic luvisols; eutric fluvisols; and eutric lepto-

sols (Table 1). The most common indigenous woody veg-

etation species in exclosures and communal grazing land

include Euclea racemosa subsp. schimperi (A.DC.)

Table 1. Basic characteristics of the exclosures and grazing land.

% coverage of soil types

Study sites Exclosure age (years) Area (ha) Eutric leptosols Chromic luvisols Eutric fluvisols

Grazing land NA 3.6 � 100 �Atikuwarit 1 2.4 � 100 �Markos 2 3.2 � 85 15

Kikibe 3 3.6 � 100 �Enkuro-fej 4 4.7 20 80 �Tinkish 5 12.7 35 65 �Deldalit 7 14.0 � � 100

Figure 1. Study area with the location of the study sites indicated in the right hand figure.

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Dandy, Calpurnia aurea (Alt.) Benth., and Dodonaea

angustifolia (L.f.). Understory vegetation of the exclo-

sures and communal grazing land were dominated by

grass species such as Hyparrhenia hirta (L.) Stapf and

Delphinium dasycaulon.

Vegetation inventory and analysis

A space-for-time substitution approach (Mekuria et al.

2011) was used to detect changes in plant species rich-

ness, diversity, and aboveground standing biomass and

carbon after conversion of communal grazing lands to

exclosures with ages of 1, 2, 3, 4, 5 and 7 years. In each

exclosure and grazing land, three transects spaced at a

minimum distance ranged from 50 to 75 m were estab-

lished. Transects were laid parallel to the topography. We

decided to delineate three transects per site because the

spatial heterogeneity of vegetation within a site was less.

Along each transect, three landscape positions (upper

slope, mid-slope, and foot slope) were delineated. At each

landscape position, a sampling plot of 20 m £ 20 m was

established (i.e., three plots per landscape position and

nine plots per site).

In each 20 m £ 20 m plot, individual plant variables

such as diameter at breast height (DBH) or, for smaller

and multi-stemmed shrubs, diameter at stump height or at

a height of 30 cm (d30) from the ground, crown diameter,

and total height were measured. DBH and d30 were mea-

sured using calipers. Crown diameter and total height

were measured using a measuring tape. The species of

plants encountered in each plot were also identified. In the

entire study, we studied 63 sample plots, of which 54

were in exclosures and nine in communal grazing land.

The average total density of plant species per hectare

was derived from the total number of individuals recorded

in the sample plots at each exclosure age (nine samples

per plot or 0.36 ha) and the communal grazing land.

Sorensen’s similarity index (Sorensen 1948) was used to

determine the species similarities among the studied sites.

The Shannon-Wiener index of diversity (H0; Shannon

1948) was used to determine native plant species diversity

in exclosures and grazing land, and to conduct compari-

sons in species diversity among the studied sites. To

determine the similarity in abundance of different species

within a community, we used the Shannon-Wiener index

of evenness (J). The types of plant species found in the

studied sites were also described in terms of richness,

plant family, and habit. Data were collected from Septem-

ber to November 2013.

Aboveground biomass and carbon estimation

To estimate aboveground biomass, dominant woody spe-

cies using our inventory data were identified (Table 2).

The dominant woody species were determined based on

the relative importance value (Mekuria et al. 2011). The

number of woody species selected for biomass estimation

varied between two and seven (Table 2). The methods of

Hoff et al. (2002) and Snowdon et al. (2002) for above-

ground woody biomass measurement were used. The

dominant woody species were grouped into three diameter

classes in order to minimize errors that can arise from var-

iable sizes of individuals (Table 2). In exclosures and the

communal grazing lands, selected individuals represent-

ing the dominant species were harvested and weighed.

Altogether we harvested 87 trees and shrubs. Fresh mass

of aboveground vegetation was adjusted to dry mass using

the measured moisture content, determined by oven dry-

ing samples at 65 �C until constant mass was attained (c.

72�78 h). Carbon stocks in aboveground biomass were

estimated by multiplying the oven-dried biomass by a fac-

tor of 0.5 (Snowdon et al. 2002).

Economic valuation

The enhancement of aboveground carbon is considered an

indirect benefit of exclosures and communal grazing land.

Necessary input factors are land and labor. As certified

emission reductions (CER) are traded as CO2 units

(UNFCCC 2003), carbon storage was converted into CO2

quantities (Mg CO2 ha¡1) multiplying carbon storage (Mg

C ha¡1) by the molar conversion factor of 3.67 (Olschew-

ski and Benitez 2005). For determining carbon revenues,

permanent carbon prices were transformed into prices for

temporary credits in accordance with Olschewski et al.

(2005) and Mekuria et al. (2011). Assuming a temporary

CER (tCER) expiring time of 5 years, an average price of

US$25 per permanent credit and a discount rate for Annex

I countries of 3%, results in a price of US$3.43 per tCER.

The labor cost of guards to protect exclosures from inter-

ference by humans and livestock was calculated as wage

per hectare based on monthly salary and the area of exclo-

sure assigned for each guard. Data on monthly salary was

obtained from the CWT. Key informant interviews was

used to gather data on major crops cultivated, crop pro-

duction, production costs, and market prices of major

crops.

A financial analysis of costs and benefits using market

prices for valuing project impacts was conducted. Given

the long-term project horizon, costs and benefits occurring

at different points of time were discounted to make them

comparable. For this purpose, real discount rate (r) was

Figure 2. Mean monthly rainfall (mm yr¡1) of the study sitesfor the years 1992 to 2006.

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determined based on price index and interest rate informa-

tion of recent 8 consecutive years (i.e., 2004�2011)

obtained from the National Bank of Ethiopia (Table 3).

We estimated the real interest rate and inflation rate using

the equation and procedures described in Mekuria et al.

(2013). We determined a nominal interest rate of 16.5%

and an average inflation rate of 14.9% based on the infor-

mation in Table 3. Consequently, the real interest rate of

(r) 5.1% was applied when discounting the monetary

values of the respective years. Net present value (NPV)

was used as a decision criterion. NPV was calculated

using the equation described in Mekuria et al. (2013).

Assessment of local community perception on exclosures

Individual household survey and key informant interviews

were conducted from September to November 2013 using

a structured survey questionnaire. Using systematic

Table 2. Dominant woody species used for aboveground biomass estimation.

Diameter class (cm)

SitesExclosureage (year) Dominant woody species

Diameterclass 1

Diameterclass 2

Diameterclass 3

Grazing land NA Croton macrostachyus Del. 2.5-13.6 13.6-24.7 24.7-35.8

Senna singueana (Del.) Lock 2.0-3.3 3.3-4.6 4.6-6.0

Calpurnia aurea (Alt.) Benth. 2.0-2.7 2.7-3.4 3.4-4.2

Atikuwarit 1 Euclea racemosa subsp. schimperi (A.DC.) Dandy 2.0-4.1 4.1-6.3 6.3-84

Calpurnia aurea (Alt.) Benth 2.0-2.9 2.9-3.9 3.9-4.8

Markos 2 Leucaena spp. 2.1-2.8 2.8-3.5 3.5-4.3

Maytenus senegalensis (Lam.) Exell 2.2-2.8 � �Calpurnia aurea (Alt.) Benth. 1.8-4.5 4.5-7.2 7.2-10

Euclea racemosa subsp. schimperi (A.DC.) Dandy 1.8-3.7 3.7-5.6 5.6-7.5

Dodonaea angustifolia (L.f.) 2.0-3.6 � �Kikibe 3 Leucaena spp. 2.0-5.3 5.3-8.6 8.6-12.0

Euclea racemosa subsp. schimperi (A.DC.) Dandy 1.0-3.3 3.3-5.6 5.6-7.9

Calpurnia aurea (Alt.) Benth. 2.0-3.4 3.4-4.8 4.8-6.2

Dodonaea angustifolia (L.f.) 2.0-3.4 3.4-4.8 4.8-6.2

Enkuro-fej 4 Leucaena spp. 2.0-5.3 5.3-8.6 8.6-12.0

Dodonaea angustifolia (L.f.) 2.0-3.0 3.0-4.0 4.0-5.0

Calpurnia aurea (Alt.) Benth. 2.0-3.7 3.7-5.4 5.4-7.2

Tinkish 5 Leucaena spp. 2.0-2.7 2.7-3.4 3.4-4.2

Euclea racemosa subsp. schimperi (A.DC.) Dandy 2.0-4.0 4.0-6.0 6.0-8.1

Dodonaea angustifolia (L.f.) 1.6-3.8 3.8-6.0 6.0-8.2

Acokanthra schimperi (A.DC.) Benth. 2.0-3.0 3.0-4.0 4.0-5.0

Calpurnia aurea (Alt.) Benth. 2.1-2.3 � �Acacia abyssinica Hochst.ex Benth. 3.2-8.2 8.2-13.2 13.2-18.2

Mytenus undata (A.DC.) f.whea 2.2-3.2 3.2-4.2 4.2-5.2

Deldalit 7 Carissa spinarum L. 2.0-2.7 2.7-3.4 3.4-4.2

Maytenus senegalensis (Lam.) Exell 2.0-3.4 3.4-4.8 4.8-6.3

Euclea racemosa subsp. schimperi (A.DC.) Dandy 2.0-3.7 3.7-5.4 5.4-7.2

Dodonaea angustifolia (L.f.) 2.0-3.1 3.1-4.2 4.2-5.6

Acokanthra schimperi (A.DC.) Benth. 2.0-4.7 4.7-7.4 7.4-10.2

Calpurnia aurea (Alt.) Benth 2.0-4.1 4.1-6.1 6.1-8.2

Leucaena spp. 2.0-3.5 3.5-5.0 5.0-6.5

Table 3. Price index and interest rates for the years 2004�2011.

Jan 04 Jan 05 Jan 06 Jan 07 Jan 08 Jan 09 Jan 10 Jan 11

General price index 89.6 100.0 112.31 131.67 190.12 206.22 223.0 297.09

Lending rate (%)

Min 7.0 7.0 7.0 8.0 8.0 8.0 7.5 7.5

Max 14.0 14.0 14.0 15.0 16.5 16.5 16.25 16.25

Mean 10.5 10.5 10.5 11.5 12.25 12.25 11.88 11.88

General price index of 2005 was used as a reference and set to 100.

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random sampling, 58 households (i.e., 16% of the water-

shed community) were selected, while 25 key informants

were selected using purposeful sampling. The key inform-

ants comprise watershed management committees, devel-

opment agents, SWC and forest use and management

experts at the district agricultural office, administration

bodies, women association committees, agricultural pro-

duction cadres, and German Development Cooperation

(GDC) focal persons. The survey questions and key infor-

mant interviews focused on the following main topics: (i)

extent, causes and consequences of land degradation as

well as the rehabilitation efforts or works in the water-

shed; (ii) exclosure establishment processes; (iii) the role

of exclosures in restoring degraded ecosystems; (iv) man-

agement, use, and protection of exclosures; and (v) infor-

mal institutions for the management, use, and protection

of exclosures.

Data analyses

We first conducted tests for normality (Kolmogorov�Smir-

nov D statistic) and equality of variance (Levene statistic)

of the variables tested. The differences among exclosures

and between an exclosure and grazing land in vegetation

parameters such as species richness, diversity, similarity in

species composition, and aboveground biomass and carbon

were assessed using one-way analysis of variance

(ANOVA). Significance of differences between treatment

means was tested using the least significant difference test

(LSD) with P < 0.05. Mean comparisons were conducted

for the variables that showed significant difference during

the analysis of variance. The qualitative data from individ-

ual interviews and key informant interviews were analyzed

using content analysis (Bernard 2006), that is, who says

what, to whom, why, to what extent, and with what effect.

Descriptive statistics was used to summarize and compare

the quantitative data from the individual interviews.

Results

Vegetation composition as affected by exclosure land

management

In exclosures, between nine and 32 plant species repre-

senting five to 21 families were recorded, whereas four

plant species representing three families were recorded in

the communal grazing land (Table 4). In all exclosures,

Fabaceae contributed the greatest number of species.

Exclosures contained more shrub, shrub/tree, and tree spe-

cies than the communal grazing land (Table 4). The num-

ber of shrub/tree and tree species increased with exclosure

duration. Except for the relatively oldest exclosures, shrub

species dominate the species composition when compared

to shrub/tree or tree species.

The similarity of vegetation composition between an

exclosure and the communal grazing land varied between

22.2% and 46.2% and decreased with exclosure age

(Table 5). In addition, the similarity of vegetation compo-

sition between the oldest exclosure and the remaining

exclosures displayed an increasing trend with exclosure

age (Table 5).

Table 4. Total number of plant species recorded in the entire sampled plots in exclosures and grazing land.

Exclosure age (year)

Variables Grazing One Two Three Four Five Seven

Total number of species recorded 4 9 9 18 14 19 32

Plant families (number) 3 6 5 12 10 14 21

Families represented by two or more species (number) 1 1 1 5 1 1 6

Climber species (number) 0 0 0 0 0 0 6

Shrub species (number) 1 2 2 4 1 1 6

Shrub/tree species (number) 1 5 5 6 4 5 9

Tree species (number) 2 2 2 8 9 13 11

Table 5. Similarities in species composition among the studied sites.

Species similarity (%)

CGL 1-yr-Exc 2-yr-Exc 3-yr-Exc 4-yr-Exc 5-yr-Exc 7-yr-Exc

CGL 46.2 30.8 36.4 33.3 34.8 22.2

1-yr-Exc 55.6 51.9 43.5 42.9 34.1

2-yr-Exc 66.7 60.9 50.0 39.0

3-yr-Exc 50.0 59.5 47.1

4-yr-Exc 60.6 39.1

5-yr-Exc 47.1

7-yr-Exc

CGL, communal grazing land; Exc, exclosure.

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Species richness, diversity, and evenness as affected by

exclosure land management

All exclosures displayed higher plant species richness

compared to the communal grazing land (Table 4). The

increases in species richness with exclosure age is not lin-

ear, as 4-year-old exclosure displayed lower species rich-

ness when compared to the 3-year-old exclosure and the

first two youngest exclosures displayed equal amounts of

species richness. Significant differences in species diver-

sity between the oldest exclosure (i.e., 7 years), and com-

munal grazing land (P D 0.01), 1- and 2-year-old

exclosures (P D 0.004 and 0.03, respectively) were

observed (Figure 3). In addition, the 3- and 5-year-old

exclosures displayed significantly higher woody species

diversity when compared to 1-year-old exclosure (P D0.03 and 0.04, respectively). Further, differences in

woody species evenness between exclosures and grazing

land as well as among the exclosures were not significant.

Aboveground standing biomass and carbon as affected

by exclosure land management

Aboveground biomass and carbon increased following the

establishment of exclosures on communal grazing land

(Figure 4). However, the increases in aboveground biomass

and carbon with exclosure age is not linear, as 2-year-old

exclosure displayed lower values compared to the 1-year-

old exclosure. In addition, the 5-year-old exclosure dis-

played equivalent aboveground biomass and carbon com-

pared to the 4-year-old exclosure (Figure 4). The amount of

aboveground carbon stored in the communal grazing land

(2.2 Mg C ha¡1, Figure 4) represents the average baseline

scenario of CER accounting of exclosure management. This

corresponds to 8.2 tons of CO2. In the Gomit watershed, 11

exclosures have been established on communal grazing

lands since 2006. Of these, three are 3-years-old, two are 5-

years-old, two are 2-years-old, two are 7-years-old, and the

remaining two are 1- and 4-years-old. We estimated that,

potentially, 51.4 Mg C ha¡1 could be sequestered from the

11 exclosures, which represents 188.6 Mg CO2 ha¡1.

Revenues from aboveground carbon sequestration

and crop production

The aboveground CO2 storage in exclosures increased

with exclosure duration (Figure 5). For calculating the

amount of temporary certificates, the baseline CO2 storage

of 8.2 Mg ha¡1 sequestered in the communal grazing land

was subtracted, resulting in tCER of 3.4, 2.1, 7.5, 12.6,

12.5, and 15.3 Mg CO2 ha¡1after 1, 2, 3, 4, 5, and 7 years,

respectively. The NPV of the aboveground carbon seques-

tered in exclosures ranged from US$6.6 to US$37.0 per

hectare, and increased with exclosure duration (Figure 5).

At a watershed level, a tCER of 139.4 Mg CO2 ha¡1 can

be obtained, resulting in NPV of US$478.3 per hectare

after 3.5 years on average.

The major agricultural crops grown in the Gomit

watershed were teff, wheat, barley, faba bean, and finger

millet. Crop productivity was highest for wheat and low-

est for teff (Table 6). Wheat production is the most attrac-

tive crop production activity generating net revenue of

US$546 per hectare (Table 6). The higher net revenue

from wheat production could arise from the relatively

higher productivity, as the costs of wheat production is

higher when compared to production costs of crops such

as teff, barley, and faba bean.

Local community perception on land degradation and

restoration efforts

The results of key informant interviews and the household

survey revealed that the majority (80%) of respondents

Figure 3. Mean (§ SE, n D 9) woody species diversity andevenness in exclosures and grazing land. Different letters in thegraph indicate significant differences at P < 0.05.

0.02.04.06.08.0

10.012.014.016.018.020.0

CGL 1-yr-Exc 2-yr-Exc 3-yr-Exc 4-yr-Exc 5-yr-Exc 7-yr-Exc

Abov

egro

und

biom

ass

and

C (t

/ha)

Sites

Aboveground biomass Aboveground C

Figure 4. Mean (§ SE, n D 9) aboveground standing biomassand carbon in exclosures and grazing land.

Figure 5. CO2 storage following the establishment of exclo-sures and the revenues generated from stored CO2.

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perceive land degradation as a problem. The most com-

mon forms of land degradation mentioned by these

respondents include soil erosion, vegetation degradation,

and decline of soil fertility in crop land. The most impor-

tant causes of land degradation mentioned by the respond-

ents include deforestation for expansion of farm land and

fuel wood, free grazing, population growth, recurrent

drought, and rainfall variability. Loss of crop land due to

gully formation, flooding in the downstream areas, and

declining crop productivity are among the consequences

of land degradation. However, few (20%) of the respond-

ents mentioned that land degradation problems are

decreasing at the moment compared to 2 to 3 years ago

due to the rehabilitation efforts undertaken in the water-

shed since 2006. Although the opinion of the respondents

over the severity of land degradation is different, all the

respondents agree on the fruitfulness of restoration efforts.

All the respondents elaborated that the restoration efforts

increased vegetation cover, rehabilitated large gullies, and

reduced loss of crops and grazing lands. The results of the

present study revealed that joint efforts among govern-

ment agencies, NGOs, and communities is crucial to

strengthen the rehabilitation efforts and further reduce the

negative consequences of land degradation.

Local community perception on exclosure land

management

Respondents elaborated that exclosures are established

with close consultations and discussion among the com-

munity, district agricultural offices, and NGOs. All of the

respondents elaborated that the decision processes in

demarcating communal grazing lands and establishing

exclosures are participatory, as the community are

involved from planning stage to monitoring and evalua-

tion of exclosure land management. However, women’s

participation in decision making is limited. Exclosures are

jointly managed by the community, CWT, and govern-

ment. The community, together with the CWT, usually

assigns guards to protect exclosures from free riders. The

exclosures are managed by the bylaws, initiated by gov-

ernment and the SUN program, and approved by the com-

munity following a discussion. The bylaw describes the

rules and regulations pertaining to the management, pro-

tection, use, and benefit sharing among the communities.

The CWT, together with government legal institution,

enforces the bylaws. All of the respondents believe that

the established bylaw is key for the sustainable manage-

ment of exclosures, as it is established through participa-

tion of the community and sets out the legal base to

impose fines on free riders. In general, the respondents

believe that CWT is effective in enforcing the bylaw.

However, some members of the CWT are reluctant to

enforce the bylaw. By failing to do so they threaten the

sustainable protection of the exclosures.

The respondents indicated that exclosures are effec-

tive in restoring degraded ecosystems, as indigenous tree

species are regenerated, vegetation cover is increased, soil

erosion and sedimentation is reduced, and gullies are reha-

bilitated following the establishment of exclosures. Fod-

der production, mainly from grasses and fodder trees such

as Sesbania have also increased following the establish-

ment of exclosures. Further, according to the respondents,

expanding exclosure establishment in the watershed bene-

fits the neighboring areas by reducing soil erosion, gully

formation, flooding, and sedimentation in the downstream

areas. With respect to the effects of exclosures on crop

production, the respondents forwarded three different

opinions: (i) the majority (82%) of the respondents men-

tioned that they had not noticed the effects of exclosures

on crop production; (ii) a few (10%) respondents men-

tioned that crop production for households having farm

plots near exclosures was reduced due to a reduction in

the size of farm plots following exclosure establishment;

and (iii) a few (8%) respondents elaborated that exclo-

sures resulted in increased crop production by reducing

soil erosion and sedimentation.

Respondents stressed that exclosure land management

reduced the availability of fuel wood, as fuel wood collec-

tion from exclosures is not permitted, and aggravated soil

and vegetation degradation in the remaining communal

grazing lands due to increased grazing and human pres-

sure. In addition, exclosure land management forced

households to reduce livestock numbers. For example,

one of the key informants observed:

Following the establishment of exclosures, I have soldthree heads and now planning to sell two heads.

However, reducing livestock numbers does not reduce

livestock productivity, as farmers are practicing stall feed-

ing of improved livestock varieties, which provide

increased milk and other livestock products.

Table 6. Major crop cultivated, crop productivity, and revenues from crop production.

Crop typeProduction

cost (ETH birr ha-1)�Production(Qt ha-1)

Output price(Birr Qt-1)

Revenue(Birr ha-1)

Net revenue(Birr ha-1)

Net revenue(US$ ha-1)

Teff 6,200 7.2 1,075 7,740 1,540 81

Wheat 7,000 25.6 679 17,382 10,382 546

Barley 3,252 20 473 9,460 6,208 327

Faba bean 1,270 13.6 606 8,241 6,972 367

Finger millet 9,800 24 763 18,312 8,512 448

�Production cost refers to the sum of the costs for ploughing, weeding, harvesting, trashing, and inputs used such as fertilizer and herbicides. Exchangerate used: 1 ETH birr D 0.0526 US$.

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The beneficiaries of a particular exclosure are house-

holds who have been using the land as communal grazing

lands. In some cases, a particular exclosure is distributed

to landless youths who are members of the watershed

community. The majority of respondents believe that

there is equal benefit sharing among the beneficiaries, as

the land area of exclosures is proportionally distributed

among the beneficiaries to harvest grasses and other prod-

ucts. However, some respondents mentioned that house-

holds without adequate labour may benefit less from grass

products compared to households who do have adequate

labour. In general, the respondents observe livelihood

changes in some households following the establishment

of exclosures through bee keeping, livestock fattening,

and increased crop production.

Discussion

The enhancement of species richness (Table 4), above-

ground biomass and carbon (Figure 4), and the significant

increase in plant species diversity (Figure 3) following the

establishment of exclosures on communal grazing lands

demonstrate that exclosures can be effective in restoring

degraded lands and ecosystem services in a relatively

short period of time. Provided that the soil types (Table 1)

and land management practices in the study sites are simi-

lar, we assumed that exclosures and communal grazing

land were comparable and that differences in the mea-

sured variables among the studied sites were caused by

land use change (i.e., exclosure establishment) and not by

inherent site variability. Such differences between exclo-

sures and grazing land can be explained in two ways. On

the one hand, increased grazing pressure in the reduced

area of communal grazing land after establishment of

exclosures and susceptibility to deforestation for fuel

wood collection would cause further vegetation degrada-

tion and decreases in aboveground biomass and carbon in

grazing land. On the other hand, the protection of exclo-

sures from human and livestock interference, and the posi-

tive consequences of increased soil moisture content due

to the construction of SWC structures would improve veg-

etation cover, composition, richness, diversity, and above-

ground biomass and carbon.

Other case studies conducted in the central and north-

ern highlands of Ethiopia have also shown that exclosures

provide favorable microhabitats for plants, which can be

an effective method to improve aboveground biomass,

density, composition, and diversity of naturally regener-

ated plant species (Mengistu et al. 2005; Abebe et al.

2006; Yami et al. 2006; Birhane et al. 2007; Mekuria and

Veldkamp 2012). In semi-arid Kenya, Mureithi (2012)

and, in China, Park et al. (2013) also reported that exclo-

sures increased woody and herbaceous species richness,

diversity, and aboveground biomass. Further, in China,

Yong-Zhong et al. (2005) demonstrated that excluding

livestock grazing enhances vegetation recovery, litter

accumulation, and development of annual and perennial

grasses. The lack of difference in species diversity

between the 1- and 2-year-old exclosures and the

communal grazing land as well as the similar species rich-

ness in the 1- and 2-year-old exclosures could indicate

that vegetation restoration through exclosure establish-

ment needs more that 2 years. The insignificant difference

in species diversity between the communal grazing land

and 4-year-old exclosures may be the result of higher

evenness of species distribution in the communal grazing

land (Figure 3), which increased the value of the Shan-

non-Wiener diversity index.

Vegetation composition, richness, diversity, and

aboveground biomass and carbon were also influenced by

exclosure age. This influence of exclosure age was sup-

ported by increased number of shrub/tree and tree species

with exclosure duration when compared to shrub species.

In addition, decreasing plant species similarity between

an exclosure and grazing land with exclosure age (Table 5)

strengthen our argument that restoration of degraded veg-

etation is influenced by exclosure duration. Further, the

observed similarities in species composition among exclo-

sures support the importance of exclosure duration in

restoring degraded vegetation through exclosure establish-

ment. The results of the present study demonstrate that all

exclosures are at early succession stage, as the vegetation

composition is dominated by shrub species. In line with

this, Park et al. (2013) demonstrated that vegetation suc-

cession following exclosure establishment proceeds via

three stages: annual plant communities; herbs; and shrubs

and trees, which illustrates the influence of exclosure

duration on woody species restoration.

The tCER net benefits from aboveground carbon

sequestration of exclosures does not provide sufficient

incentive to initiate the participation of land managers and

local communities in establishing further exclosures in

the future. However, if all ecosystem services from exclo-

sures such as soil carbon sequestration, soil nutrient resto-

ration, and honey and grass production are accounted for,

exclosures can be a competitive form of land use manage-

ment when compared to crop production. Mekuria et al.

(2011) have reported a similar result in which tCER net

benefits of exclosure only cover 44% of the benefits from

the best alternative land use. However, this study further

demonstrates that exclosures can be a competitive form of

land use if all ecosystem services are considered and

traded, and could generate a 28% higher NPV when com-

pared to the best alternative land use over a 30 year

period.

Although our results clearly show that exclosures as

carbon sink projects are economically unattractive at an

average price of US$25 per permanent credit, they could

be viable alternatives if the price per permanent credit

increases to US$80. Using a price of US$80 per perma-

nent credit (US$10.99 per temporary credit), the NPV

from aboveground carbon storage of the relatively older

exclosures (i.e., 4- to 7-year-old) ranged from US$117 to

US$118.5 per hectare, which is higher than the net reve-

nues from teff production (Table 6). Thus, prices that are

equal or greater than US$80 per permanent credit would

make the relatively older exclosures profitable when com-

pared to teff production without considering payments for

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other ecosystem services obtained from exclosures

establishment.

Compared to the average annual income of the com-

munities in the Gomit watershed (i.e., ETB 1671), the

contribution of the potential income that can be generated

from carbon trading is considerable (i.e., 42.1% of the

annual income). This in turn suggests that establishing

exclosures on communal grazing lands could help achieve

increases in annual household income and improve the

livelihoods of the smallholders. This is also consistent

with communities’ perception of the importance of exclo-

sures in improving livelihoods.

The use of participatory decision-making processes in

the rehabilitation of degraded ecosystems through exclo-

sures establishment, legalizing the watershed community

on the use, protection and management of natural resour-

ces, developing agreed bylaws, and establishing a strong

CWT facilitated the sustainable management of exclo-

sures in the watershed. In addition, the positive attitudes

of the community toward the effectiveness of exclosures

in restoring degraded ecosystems provide incentives to

maximize the benefits. Although the respondents agree

with the importance of exclosures in enhancing fodder

production and other services, they put forward three dif-

ferent opinions on the influence of exclosures on crop pro-

duction. This difference could arise from the location of

farm lands, and level of awareness and understanding of

the ongoing rehabilitation efforts.

The limited participation of women in decision-mak-

ing in exclosure land management can be attributed to

poor representation of women in the CWT (just two out of

nine CWT members were women). In addition, local cul-

tural perceptions that precluded women’s participation in

watershed management decisions and that do not allow

women to express their opinions in a public situation

could contribute to their limited participation in decision-

making. This suggests that greater inclusion of women

and marginal groups is needed to understand the different

priorities, concerns, preferences, and interests of men and

women farmers in order to achieve sustainable exclosure

land management.

Sustainable watershed management such as establish-

ing exclosures and enhancing natural regeneration of

woody species through constructing SWC structures in

exclosures can be used to reverse land degradation, lower

environmental impacts, and diversify household income

sources. Exclosures help achieve sustainable intensifica-

tion of agricultural production by reducing soil erosion,

improving vegetation cover, and sequestering CO2 and

are therefore an adaptive strategy to climate change or

variability. Exclosures can also generate up to 42% of the

current annual income of the communities in the study

sites if carbon stored in aboveground biomass is traded.

This in turn opens up possibilities to expand exclosures in

the watershed for the restoration of degraded lands and

diversify household income sources. The positive opin-

ions of watershed communities on exclosure land manage-

ment could be used as an asset for the expansion of

exclosures in the watershed.

However, the concerns of the local communities,

particularly the negative effects of exclosures in fuel

wood availability and the severe degradation of useful

tree and shrub species in the remaining communal graz-

ing lands is critical, as more than 90% of local communi-

ties depend on bioenergy sources (wood, dung) to meet

their household energy demands (Zenebe 2007). This

illustrates that the sustainability of exclosure land man-

agement can be attained only if these critical concerns

are addressed by a joint effort among government agen-

cies, NGOs, and communities. In addition, government

authorities (i.e., Bureau of Agriculture, district agricul-

tural offices and district administrative bodies) can help

strengthen participatory decision-making in exclosure

land management to include the voices of women and

other marginal groups.

Conclusions

The results of this study confirm that the establishment of

exclosures on degraded communal grazing lands in the

Gomit watershed can effectively restore degraded ecosys-

tems, diversify household income, and contribute to improv-

ing the livelihood of smallholders. However, the decision to

establish additional exclosures should include a comprehen-

sive socioeconomic analysis that incorporates all services

provided by exclosures. In addition, local communities’

concerns on the expansion of exclosures should be

addressed. In order to address local communities’ concerns,

the government could exert efforts toward enhancing the

awareness of communities on the importance of sustainable

land management, while NGOs could provide credit to

expand bee keeping and livestock fattening programs, and

introduce solar panels in the watershed. Communities could

contribute local knowledge of land management, labor, and

locally available materials.

Acknowledgements

We are grateful to the Amhara Regional Agricultural ResearchInstitute (ARARI) for their cooperation and facilitation of theresearch work. We are also very grateful to the local communi-ties in the study area and the CWT for their support during thefieldwork.

Note

1. Woina dega (subtropical zone) includes the highlands areasof 1830�2440 m above sea level with a mean annual tem-perature of c. 22 �C and annual rainfall between 510 and1530 mm.

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