The effects of forest conversion on annu
Agriculture, Ecosystems and Environment 69 (1998) 17±26
The effects of forest conversion on annual crops and pastures:
Estimates of carbon emissions and plant species
loss in a Brazilian Amazon colony
S. Fujisakaa,*, C. Castillab, G. Escobara, V. Rodriguesc,
E.J. Veneklaasa, R. Thomasa, M. Fishera
a
Centro Internacional de Agricultura Tropical (CIAT), A.A. 6713, Cali, Colombia
b
International Centre for Research in Agroforestry (ICRAF), Kenya
c
Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA), Brazil
Abstract
The municipality of Theobroma in Rondonia, Brazil, covers 2165 km2, of which 43% was deforested by 1993. Between 1973
and 1993, the national government continued to improve highway BR364 connecting the area to Brazil's south-central region
and established a colony in Theobroma. During this period, 98% of the deforestation occurred. Some 1800 settler families
continue to convert forest into pasture in a system based on the slash-and-burn agriculture and dual-purpose cattle production.
Trends in carbon emissions and plant species losses during the 20-year history of Theobroma were analyzed by combining
observed shifts in land-use types with estimates for the carbon stocks and plant species richness of each of these types. Carbon
stocks declined from about 200 t haÿ1 in the forest to 28 t haÿ1 in the pasture and of 326 plant species encountered in the
forest, only 20 remained in pastures (along with 66 species not found in forests). The effects of converting more than 93 000 ha
of forest into other uses over 20 years include approximate losses of 14 million tons of C to the atmosphere and substantial
losses of plant species. Land use alternatives that would store more C include agroforestry and ± given the strong incentives
for settlers to convert lands into pasture ±improving pasture management or developing silvopastoral systems. Plant species
conservation may be improved with proposed ways to add private value to the forest. # 1998 Elsevier Science B.V. All rights
reserved.
Keywords: Plant biodiversity; Carbon emissions; Slash-and-burn agriculture; Tropical deforestation
1. Introduction
The two main sources of greenhouse gas emissions
are fossil fuel consumption and agricultural practices.
*Corresponding author. Tel.: 00 57 2 4450 000; fax: 00 57 2
4450 073; e-mail: s.fujisaka@cgnet.com
0167-8809/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved.
PII S0167-8809(98)00091-7
One third of the emissions from agricultural practices
are associated with land clearing, principally deforestation in the tropics (Duxbury et al., 1993). Tropical
deforestation is thought to release about 1.5±3.0 Gt
C yrÿ1 as CO2 or about 10±14% of global C emissions
(Houghton, 1991 and Gifford, 1994). For all the
greenhouse gas emissions (CO2, CH4, NOx and chloro-
18
S. Fujisaka et al. / Agriculture, Ecosystems and Environment 69 (1998) 17±26
¯uorocarbons), land clearing is thought to comprise
about 8% of the total (Duxbury et al., 1993). Globally,
the Amazon represents the world's largest remaining
tropical forest and suffers the highest deforestation
rates. Analysis of satellite images indicates that up to
10% of the 4 million km2 of Brazil's originally
forested Amazon was cleared by 1991 (Fearnside,
1993 and Moran et al., 1994). Government policies
to build roads, establish colonies and provide incentives for cattle ranching (Fujisaka et al., 1996) have
spurred deforestation of the Brazilian Amazon (which
holds 55% of the Amazon). Within the area, deforestation has been highest (in terms of percentage of
original forest lost) in the states of Maranhao, Tocantins, Mato Grosso and Rondonia (Fearnside, 1993),
while recent rates have been highest in Rondonia and
Mato Grosso (Anderson, 1990).
Theobroma is a municipality and a colony of Rondonia along the highway BR364, which now connects
the area to Cuiaba and the south-central region of
Brazil and, to the west, to Acre as far as Rio Branco.
Established some 25 years ago, the colony covers
2165 km2 and was 43% deforested by 1993. Colonists
®rst clear the forest for slash-and-burn agriculture then
largely establish pastures rather than fallow and eventually re-crop lands. Colonists do not practice shifting
cultivation as such. Theobroma represents 0.4% of the
area of the state of Rondonia, which (statewide) was
17% deforested by 1993.
The climate of this region in Rondonia is of the Am
type (KoÈppen classi®cation) with an average temperature of 248C and annual rainfall of 2000±2250 mm
(RADAMBRASIL, 1978). The months of June, July
and August form a distinct dry season. Soils of the
sampled sites are Oxisols and Ultisols with low fertility and high aluminium saturation (RADAMBRASIL, 1978).
This paper examines two of the environmental
impacts of deforestation ± estimated C emissions
and decreases in plant diversity. Data gathered were
C stocks under different land uses, plant species under
the same land uses and colonists' land uses. Secondary
data on deforestation in the municipality were also
obtained. This paper estimates total C emissions,
discusses the implications of plant diversity losses
and offers some potential alternatives that would store
more C and decrease deforestation and the resulting
species losses.
2. Methods
2.1. Carbon
Carbon was measured above and below ground in
forest, newly cleared and burned cropland, fallows of
2±3 years and in pastures (largely of Brachiaria
decumbens and Brachiaria brizantha with a mean
age of about 10 years). At each of the two sites and
for each of the different land uses, ®ve 100 m2
(425 m) transects were sampled. For aboveground
C measurements, live and dead trees, logs, understorey
and litter were sampled. Live tree biomass was estimated based on the diameter of trees (>2.5 cm) at
breast height using a published allometric relationship
(Brown et al., 1989). Carbon stocks in standing or
fallen logs were estimated based on length, mean
diameter and a density of 0.4 g cmÿ3. Understorey
C was measured for two 1 m2 quadrats within each
transect. Surface litter was collected from the same
transects to the depth of the mineral soil (Anderson
and Ingram, 1993). The biomass of surface litter was
corrected following ashing. It was assumed that all the
biomass pools contained 48% C (Castilla, 1992 and
Yvan Biot 1996, personal communication).
Below-ground pools included roots and soil organic
C. Samples were taken at 0±20 and 20±40 cm depths.
A 202020 cm sample was taken from each litter
quadrat; a 2 kg sub-sample was taken and roots
removed from the remainder by washing over a
1 mm sieve. Roots were oven dried and ashed and
C estimated. Soil sub-samples were air dried, sieved
through a 2 mm mesh and measured for C by wet
oxidation (Anderson and Ingram, 1993). Large structural roots were not included in the sampling and could
be a source of some C underestimation. Soil organic
contents were corrected for bulk density taken from
undisturbed samples.
2.2. Plant species and community change
Species composition was determined for the following communities: forest, the ®rst year of cropping
after forest clearing, fallowed ®elds and pasture
(again, of Brachiaria sp. and of an approximate 10year mean age). Six transects were sampled for each
land use except pastures. In each transect, ten 4 m2
plots were sampled with a 5 m distance between each
19
S. Fujisaka et al. / Agriculture, Ecosystems and Environment 69 (1998) 17±26
and the number of individuals per species recorded.
The point-quadrat method (Mueller-Dombois and
Ellenberg, 1974) was used to sample pastures in ®ve
20 m transects on eight ®elds, sampling every 20 cm,
yielding percentage cover per species.
A local forest expert (matero) helped identify species to local and, in many cases, scienti®c name.
Botanists at the herbariums of the Fundacao de Tecnologia do Estado do Acre (FUNTAC) and the Universidad Federal del Estado de Acre (UFAC), Rio
Branco, helped obtain additional scienti®c names.
Nomenclature follows the Index Kewensis (Royal
Botanic Gardens, 1993). Of all the species, 88% could
be identi®ed to family, 53% to genus and 28% to
species levels. Species were classi®ed as trees, shrubs
(species with maximum height
The effects of forest conversion on annual crops and pastures:
Estimates of carbon emissions and plant species
loss in a Brazilian Amazon colony
S. Fujisakaa,*, C. Castillab, G. Escobara, V. Rodriguesc,
E.J. Veneklaasa, R. Thomasa, M. Fishera
a
Centro Internacional de Agricultura Tropical (CIAT), A.A. 6713, Cali, Colombia
b
International Centre for Research in Agroforestry (ICRAF), Kenya
c
Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA), Brazil
Abstract
The municipality of Theobroma in Rondonia, Brazil, covers 2165 km2, of which 43% was deforested by 1993. Between 1973
and 1993, the national government continued to improve highway BR364 connecting the area to Brazil's south-central region
and established a colony in Theobroma. During this period, 98% of the deforestation occurred. Some 1800 settler families
continue to convert forest into pasture in a system based on the slash-and-burn agriculture and dual-purpose cattle production.
Trends in carbon emissions and plant species losses during the 20-year history of Theobroma were analyzed by combining
observed shifts in land-use types with estimates for the carbon stocks and plant species richness of each of these types. Carbon
stocks declined from about 200 t haÿ1 in the forest to 28 t haÿ1 in the pasture and of 326 plant species encountered in the
forest, only 20 remained in pastures (along with 66 species not found in forests). The effects of converting more than 93 000 ha
of forest into other uses over 20 years include approximate losses of 14 million tons of C to the atmosphere and substantial
losses of plant species. Land use alternatives that would store more C include agroforestry and ± given the strong incentives
for settlers to convert lands into pasture ±improving pasture management or developing silvopastoral systems. Plant species
conservation may be improved with proposed ways to add private value to the forest. # 1998 Elsevier Science B.V. All rights
reserved.
Keywords: Plant biodiversity; Carbon emissions; Slash-and-burn agriculture; Tropical deforestation
1. Introduction
The two main sources of greenhouse gas emissions
are fossil fuel consumption and agricultural practices.
*Corresponding author. Tel.: 00 57 2 4450 000; fax: 00 57 2
4450 073; e-mail: s.fujisaka@cgnet.com
0167-8809/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved.
PII S0167-8809(98)00091-7
One third of the emissions from agricultural practices
are associated with land clearing, principally deforestation in the tropics (Duxbury et al., 1993). Tropical
deforestation is thought to release about 1.5±3.0 Gt
C yrÿ1 as CO2 or about 10±14% of global C emissions
(Houghton, 1991 and Gifford, 1994). For all the
greenhouse gas emissions (CO2, CH4, NOx and chloro-
18
S. Fujisaka et al. / Agriculture, Ecosystems and Environment 69 (1998) 17±26
¯uorocarbons), land clearing is thought to comprise
about 8% of the total (Duxbury et al., 1993). Globally,
the Amazon represents the world's largest remaining
tropical forest and suffers the highest deforestation
rates. Analysis of satellite images indicates that up to
10% of the 4 million km2 of Brazil's originally
forested Amazon was cleared by 1991 (Fearnside,
1993 and Moran et al., 1994). Government policies
to build roads, establish colonies and provide incentives for cattle ranching (Fujisaka et al., 1996) have
spurred deforestation of the Brazilian Amazon (which
holds 55% of the Amazon). Within the area, deforestation has been highest (in terms of percentage of
original forest lost) in the states of Maranhao, Tocantins, Mato Grosso and Rondonia (Fearnside, 1993),
while recent rates have been highest in Rondonia and
Mato Grosso (Anderson, 1990).
Theobroma is a municipality and a colony of Rondonia along the highway BR364, which now connects
the area to Cuiaba and the south-central region of
Brazil and, to the west, to Acre as far as Rio Branco.
Established some 25 years ago, the colony covers
2165 km2 and was 43% deforested by 1993. Colonists
®rst clear the forest for slash-and-burn agriculture then
largely establish pastures rather than fallow and eventually re-crop lands. Colonists do not practice shifting
cultivation as such. Theobroma represents 0.4% of the
area of the state of Rondonia, which (statewide) was
17% deforested by 1993.
The climate of this region in Rondonia is of the Am
type (KoÈppen classi®cation) with an average temperature of 248C and annual rainfall of 2000±2250 mm
(RADAMBRASIL, 1978). The months of June, July
and August form a distinct dry season. Soils of the
sampled sites are Oxisols and Ultisols with low fertility and high aluminium saturation (RADAMBRASIL, 1978).
This paper examines two of the environmental
impacts of deforestation ± estimated C emissions
and decreases in plant diversity. Data gathered were
C stocks under different land uses, plant species under
the same land uses and colonists' land uses. Secondary
data on deforestation in the municipality were also
obtained. This paper estimates total C emissions,
discusses the implications of plant diversity losses
and offers some potential alternatives that would store
more C and decrease deforestation and the resulting
species losses.
2. Methods
2.1. Carbon
Carbon was measured above and below ground in
forest, newly cleared and burned cropland, fallows of
2±3 years and in pastures (largely of Brachiaria
decumbens and Brachiaria brizantha with a mean
age of about 10 years). At each of the two sites and
for each of the different land uses, ®ve 100 m2
(425 m) transects were sampled. For aboveground
C measurements, live and dead trees, logs, understorey
and litter were sampled. Live tree biomass was estimated based on the diameter of trees (>2.5 cm) at
breast height using a published allometric relationship
(Brown et al., 1989). Carbon stocks in standing or
fallen logs were estimated based on length, mean
diameter and a density of 0.4 g cmÿ3. Understorey
C was measured for two 1 m2 quadrats within each
transect. Surface litter was collected from the same
transects to the depth of the mineral soil (Anderson
and Ingram, 1993). The biomass of surface litter was
corrected following ashing. It was assumed that all the
biomass pools contained 48% C (Castilla, 1992 and
Yvan Biot 1996, personal communication).
Below-ground pools included roots and soil organic
C. Samples were taken at 0±20 and 20±40 cm depths.
A 202020 cm sample was taken from each litter
quadrat; a 2 kg sub-sample was taken and roots
removed from the remainder by washing over a
1 mm sieve. Roots were oven dried and ashed and
C estimated. Soil sub-samples were air dried, sieved
through a 2 mm mesh and measured for C by wet
oxidation (Anderson and Ingram, 1993). Large structural roots were not included in the sampling and could
be a source of some C underestimation. Soil organic
contents were corrected for bulk density taken from
undisturbed samples.
2.2. Plant species and community change
Species composition was determined for the following communities: forest, the ®rst year of cropping
after forest clearing, fallowed ®elds and pasture
(again, of Brachiaria sp. and of an approximate 10year mean age). Six transects were sampled for each
land use except pastures. In each transect, ten 4 m2
plots were sampled with a 5 m distance between each
19
S. Fujisaka et al. / Agriculture, Ecosystems and Environment 69 (1998) 17±26
and the number of individuals per species recorded.
The point-quadrat method (Mueller-Dombois and
Ellenberg, 1974) was used to sample pastures in ®ve
20 m transects on eight ®elds, sampling every 20 cm,
yielding percentage cover per species.
A local forest expert (matero) helped identify species to local and, in many cases, scienti®c name.
Botanists at the herbariums of the Fundacao de Tecnologia do Estado do Acre (FUNTAC) and the Universidad Federal del Estado de Acre (UFAC), Rio
Branco, helped obtain additional scienti®c names.
Nomenclature follows the Index Kewensis (Royal
Botanic Gardens, 1993). Of all the species, 88% could
be identi®ed to family, 53% to genus and 28% to
species levels. Species were classi®ed as trees, shrubs
(species with maximum height