Report
L.J. Gorenflo and Katrina Brandon
Agricultural Capacity and Conservation
in High Biodiversity Forest Ecosystems
Agricultural development is a leading cause of habitat
destruction that increasingly threatens global biodiversity.
To help understand the likelihood and implications of
agricultural expansion in areas of high conservation
importance, this article examines agricultural suitability
in forested portions of biodiversity hotspots and tropical
wilderness areas, regions with especially rich concentrations of species found nowhere else. The study employs
geographic information system technology to examine
suitability for six crop categories in selected conservation
localities worldwide: those portions of regions containing
high biodiversity, protected areas (e.g. national parks)
within these regions, and 10-km bands around the
protected areas that are dominated by forest. Analyses
reveal low suitability for most crop categories under both
commercial and subsistence scenarios, with a few exceptions. In most cases, adequate planning can enable
the coexistence of agriculture and biodiversity without
compromising either.
INTRODUCTION
At the onset of the 21st century, the disappearance of minimally
1000 species annually marks mass extinction of a magnitude
virtually unknown in the earth’s history (1–3). A leading cause
of rapid biodiversity loss is habitat destruction, much of which
is due to widespread agricultural development (4–8). With continued growth in human population anticipated over coming
decades in much of the world (9), and increasing per capita
demand and land degradation (10–12), agricultural expansion is
certain to continue (13). The final two decades of the 20th
century reveal the magnitude of modern agricultural impacts.
Land used for crop production during this period increased
roughly 130 000 km2 yr 1 (14), with much of this expansion
occurring in natural forests, particularly important repositories
of biodiversity (8).
Forest ecosystems contain more biodiversity than other
terrestrial ecosystems (15). This biodiversity occurs at the ecosystem, species, and genetic levels. As key repositories of
biodiversity, forest ecosystems play an important role in conservation. Biologists have identified regions with exceptional
concentrations of endemic species (species found nowhere else),
the hotspots and tropical wilderness areas that guide many global
conservation efforts (16–18). Most of these regions contain
forests—habitats of considerable value for conservation, the
loss of which to agricultural expansion, or any form of development, would be particularly costly to biodiversity.
This study examined the agricultural suitability of forested
lands in regions particularly rich in biodiversity to assess their
potential contribution to crop production were they converted
to agriculture. Deforestation can occur for a variety of reasons
(19–27), although the process often involves either initial timber
harvest and subsequent agricultural development or clearing
solely for agriculture. As the demand for food and marketable
agricultural commodities increases, land with high productivity
potential becomes increasingly vulnerable to conversion for crop
production—in the case of forested areas, possibly providing an
Ambio Vol. 34, No. 3, May 2005
additional impetus beyond harvesting trees for habitat conversion. The study relies on agricultural suitability estimates
recently generated by the Global Agro-Ecological Zones
(GAEZ) assessment (28) and employs geographic information
system technology to assess agricultural capacity in forested
portions of high biodiversity regions around the world. The
ultimate aims of this study are two. One is to evaluate the impact
of conservation on subsistence and commercial agricultural
development in biodiversity-rich forested ecosystems—that is, to
assess the agricultural potential unrealized by not converting
forests to crop production. The second is to provide a foundation
from which conservationists can engage planners, agro-industry
representatives, commercial and subsistence agriculturalists, and
other decision makers in rural sector land-use planning that
considers the benefits of conserving forests compared with
converting them to agricultural production.
MATERIALS AND METHODS
Assessing agricultural potential for forested portions of biodiversity regions is possible thanks to the availability of global
digital data on forest (and other) ecosystems, agricultural suitability, biodiversity regions, and protected areas. The analyses
that follow involve the calculation of summary statistics on
agricultural suitability for forested portions of biodiversity regions and areas within them. Because the databases examined
are georeferenced—that is, they have associated geographic
coordinates—they can be mapped and overlain on one another,
enabling the analysis of relationships between them using geographic information system technology.
This study focuses on forested portions of biodiversity
hotspots and tropical wilderness areas. Hotspots are regions
containing exceptionally high concentrations of endemic species
also marked by high habitat loss (18). Although they cover only
about 1.4% of the earth’s land surface, the 25 hotspots considered
in this study contain as much as 44% of the earth’s vascular plants
and 35% of all species in four vertebrate groups (29). A large
number of human inhabitants and generally rapid population
and household growth place hotspots under increasing stress
(30, 31), underscoring the importance of conservation activities
there. Tropical wilderness areas, in turn, comprise expanses of
tropical forest containing high concentrations of endemic
species, retaining minimally 70% of their primary vegetation,
and generally averaging fewer than five persons km 2 (16, 17).
Working in biodiversity hotspots and tropical wilderness areas
focuses conservation efforts on those regions where they likely
will affect the greatest amount of biodiversity.
Most forested subsections of regions with high biodiversity
likely represent intact habitat and, consequently, contain
considerable biodiversity in addition to providing a range of
key ecosystem services (32–36). Remotely sensed satellite
imagery, which contributed to several of the data sets used
directly or indirectly in this study, enabled the identification of
forest ecosystems in 2000. Here, we defined forests based on the
Global Land Cover 2000 database (37) and included all areas
categorized as some form of forest (38).
The analyses reported in this study used the recently released
GAEZ assessment of global agricultural capabilities (28). That
project examined a range of digital data that became available on
a global scale during the 1990s for the key agricultural variables of
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soil, terrain, and climate. The GAEZ researchers used these data
to assemble a land resources database, which formed the first key
component of their study. The second key component of the
GAEZ assessment was a database of land utilization types—
agricultural production systems with crop-specific environmental
requirements under certain input and management criteria. The
land utilization types identified by the GAEZ project consisted of
154 crop, fodder, and pasture land utilization types defined for
high (commercial), intermediate (commercial-subsistence), and
low (subsistence) input management or cropping scenarios. By
matching the requirements of land utilization types with the land
resources for a particular locality, the GAEZ assessment produced a global database of agronomically attainable yields by
grid cell for specific cropping systems. One outcome of the GAEZ
assessment was a georeferenced, gridded database with a 5 0 longitude/latitude resolution (grid cells approximately 9 km square)
estimating the suitability for various crops or crop categories
under low-, intermediate-, and high-input cropping scenarios.
This study employed World Database on Protected Areas
Consortium (WDPAC) data on protected areas (e.g. national
parks) for the world, recently released at the World Parks
Congress in September 2003 (39). This study examined 6183
geographic localities representing partial or entire protected
areas in the WDPAC database lying in forested portions of
biodiversity hotspots and tropical wilderness areas, as determined by the Global Land Cover 2000 data.
To explore the relationship between agricultural capacity
and conservation in forest ecosystems, we analyzed three geographic entities: forested portions of entire hotspots and
tropical wilderness areas, protected areas within forested portions of these high biodiversity regions, and 10-km-wide buffers
surrounding protected areas in forested portions of high
biodiversity regions. The forested portions of entire hotspots
and tropical wilderness areas represent some of the most
biodiversity-rich subsections of regions themselves defined in
large part based on their high biodiversity (Fig. 1). Forested
protected areas comprise important repositories of biodiversity
in regions that often have experienced considerable habitat loss,
localities of particular importance to conservation that usually
greatly restrict or completely prohibit agricultural activity.
Finally, forested 10-km buffers provide both key ecological
services to associated protected areas as well as some measure of
protection for those protected areas from encroaching human
impact. In conducting this study, we considered only those
portions of a protected area or buffer categorized as forested; if
part of a protected area or buffer was not covered by forest, we
excluded that part from our analysis. In addition, we removed
portions of protected areas or buffers extending into ocean to
exclude areas inherently incapable of agricultural production.
Because of the geographic breadth of this study, we considered a range of crops and crop categories, defined as follows:
–
–
–
–
–
–
Cereals (barley, maize, millet, rice, rye, sorghum, and wheat)
Cotton (used as a surrogate for fiber crops)
Pulses (chickpea, cowpea, phaseolus bean, and soybean)
Roots/tubers (cassava, sweet potato, and white potato)
Oil crops (groundnut, oil palm, olive, rape, and sunflower)
Sugar crops (sugar beet and sugar cane)
The analysis incorporated two cropping scenarios reflecting
differing input and management levels: high and intermediate.
The high-input cropping scenario represents the advanced
management assumption used by the GAEZ assessment. Synonymous with commercial production, high inputs consist of
fully mechanized production with low labor intensity, improved
yield crop varieties, and optimal applications of fertilizers and
chemical disease, pest, and weed control. Intermediate inputs, in
turn, represent subsistence production plus some production for
commercial sale. Intermediate input assumes medium-intensive
labor (largely manual, augmented with some animal traction or
mechanization), improved crop varieties, and some application
of fertilizer and chemical pesticides (28). The intermediate
scenario entails best-case conditions for subsistence agriculture.
Results of the analyses conducted for this study appear in the
form of mean suitability indices. The GAEZ measured suitability
for each 5 0 grid cell as the percentage of documented maximum
yield for a particular crop category under a specified inputmanagement scenario—for instance, the amount of cereals that
can be produced under high inputs in a particular cell compared
with the maximum level of cereal production observed globally
under high inputs. Index values ranged from 0.0 to 100.0, which
Figure 1. Forested portions of
hotspots and tropical wilderness
areas. (1: Atlantic Forest, 2: Brazilian Cerrado, 3: California Floristic Province, 4: Cape Floristic
Province, 5: Carribean, 6: Caucasus, 7: Central Chile, 8: ChocoDarien-Western Ecuador, 9: Eastern Arc Mountains and Coastal
Forests, 10: Guinean Forests of
West Africa, 11: Indo-Burma, 12:
Madagascar and Indian Ocean
Islands, 13: Mediterranean Basin,
14: Mesoamerica, 15: Mountains
of South Central China, 16: New
Caledonia, 17: New Zealand,
18: Philippines, 19: Polynesia
and Micronesia, 20: Southwestern Australia, 21: Succulent Karoo, 22: Sundaland, 23: Tropical
Andes, 24: Wallacea, 25: Western
Ghats and Sri Lanka, 26: Amazon
Wilderness Area, 27: Congo Wilderness Area, 28: New Guinea
Wilderness Area; data sources:
forested sections of biodiversity
regions derived from reference
37, hotspot and tropical wilderness area boundaries obtained
from Conservation International). Note that although all hotspots and wilderness areas
contained forest in 2000, some
forested sections were so small
that they do not show up clearly
on a map of this scale.
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Ambio Vol. 34, No. 3, May 2005
GAEZ researchers used to define the following eight agricultural suitability categories:
– Very high, suitability index . 85% of maximum yield, index
value = 1
– High, suitability index = 70%–85% of maximum yield, index
value = 2
– Good, suitability index = 55%–70% of maximum yield, index
value = 3
– Medium, suitability index = 40%–55% of maximum yield,
index value = 4
– Moderate, suitability index = 25%–40% of maximum yield,
index value = 5
– Marginal, suitability index = 5%–25% of maximum yield,
index value = 6
– Very marginal, suitability index = 0%–5% of maximum yield,
index value = 7
– Unsuitable, suitability index = 0% of maximum yield, index
value = 8
RESULTS
The analyses conducted in this study yielded mean suitability
values for each of six geographic entity–cropping combinations
(Fig. 2). With few exceptions, the results indicate relatively low
agricultural suitability for forested portions of biodiversity
regions, forested protected areas within those regions, and
forested portions of 10-km buffers around protected areas. The
vast majority of the three geographic entities we examined
register unsuitable, very marginal, or marginal suitability. Only
under the high-input cropping scenario do mean suitability
estimates enter the good category, and then for very few crop
categories and geographic areas.
Figure 3 presents highest mean suitability categories for each
geographic entity–input combination. Most intermediate-input
results fall into unsuitable (21.0%), very marginal (39.5%), and
marginal (29.6%) suitability categories. Stated differently, if one
focuses solely on the most suitable crop categories in forested
portions of biodiversity regions under intermediate inputs, about
Figure 2. Agricultural suitability results for forested portions of biodiversity regions, protected areas, and 10-km buffers around protected
areas.
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9 of 10 combinations have expected yields less than 25% of
potential maximums (moderate suitability or less). The results of
high-input scenarios are slightly better than their intermediate
counterparts. The majority once again falls into unsuitable
(23.5%), very marginal (24.7%), and marginal (29.6%) suitability
categories, although certain crop categories attain moderate
(12.3%), medium (8.6%), and good (1.3%) suitability. For both
cropping scenarios, cereals most often produced the highest
agricultural suitability.
Because subsistence and commercial agriculturalists ultimately must cultivate the land available to them, land with low
agricultural suitability can still be desirable for growing crops if
it is more productive than other land nearby. Although we cannot consider all local opportunities for agricultural development
in a global study, we can shed some light on relative suitability
through a series of comparisons among results of our analyses.
At the large geographic scale, forested components of the hotspots and tropical wilderness areas tend to have lower agricultural suitability than entire hotspots and wilderness areas under
both intermediate and high cropping input scenarios (Fig. 4,
comparisons 1 and 6). Exceptions tend to reveal modest advantages, apart from the Polynesia/Micronesia hotspot where for
many crops forested subsections are a full suitability category
better than the entire biodiversity region, and for pulses where
for many biodiversity regions forested subsections similarly
show a full suitability category of improvement over the region
as a whole. At a smaller scale, forested portions of protected
areas and forested 10-km buffers around them also tend to have
less agricultural capacity than entire hotspots and tropical
wilderness areas, again under both intermediate (Fig. 4,
comparisons 2 and 3) and high (Fig. 4, comparisons 7 and 8)
cropping input scenarios. Furthermore, forested portions of
protected areas and forested buffers around them tend to be less
suitable for agriculture than the entire forested portions of the
hotspots and wilderness areas that contain them, under both
cropping input scenarios (Fig. 4, comparisons 4 and 5 and 9 and
10). This finding of lower suitability for forested protected areas
and buffers is consistent with the evaluation of agricultural
productivity for entire protected areas and buffers located in
hotspots and tropical wilderness areas (40)—arguing that the
lost opportunity for crop production due to conservation is low
in both absolute and relative terms.
There are a few exceptions to the tendencies we identified
earlier for low agricultural suitability in forested portions of
regions rich in biodiversity. Under the intermediate cropping
input scenario, the highest mean agricultural suitability achieved
is medium, which occurs for at least one crop category–geographic entity combination in the Brazilian Cerrado, Eastern Arc
and Coastal Forests, and West African Forests hotspots. These
results are generally consistent with the tendency for low agricultural suitability documented throughout this study. However,
when one considers the high cropping input scenario, mean suitability increases to good levels for a few crop category–geographic
entity combinations in forested portions of the Amazon and
Congo tropical wilderness areas and the Brazilian Cerrado hotspot. Such suitability values indicate localities amenable to
commercial agriculture. This activity is already well established
throughout much of the Brazilian Cerrado (41, 42). If agricultural
suitability plays a role in agricultural expansion, current
agricultural patterns in the Cerrado may provide a disturbing
preview of coming development in remaining forested areas in the
Cerrado (a region largely dominated by grassland) and other
biodiversity regions with similar agricultural suitability.
The high agricultural suitability of forested portions of the
Amazon and Congo is particularly concerning for conservation.
Broad expanses of primary forest habitat characterize both of
these regions, a key reason for their important roles in global
conservation. The presence of high agricultural suitability likely
Figure 3. Maximum agricultural suitability estimates for each hotspot or wilderness area. (Suitability indices: 1 = very high; 2 = high;
3 = good; 4 = medium; 5 = moderate; 6 = marginal; 7 = very marginal; 8 = unsuitable.)
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Figure 4. Comparisons of agricultural suitability estimates for the following areas: 1. Entire hotspots/wilderness areas (‘‘larger area’’ in
legend) vs. forested portions of hotspots/wilderness areas, rain-fed/intermediate inputs. 2. Entire hotspots/wilderness areas (‘‘larger area’’)
vs. forested portions of protected areas, rain-fed/intermediate inputs. 3. Entire hotspots/wilderness areas (‘‘larger area’’) vs. forested portions
of 10-km buffers around protected areas, rain-fed/intermediate inputs. 4. Forested portions of hotspots/wilderness areas (‘‘larger area’’) vs.
forested portions of protected areas, rain-fed/intermediate inputs. 5. Forested portions of hotspots/wilderness areas (‘‘larger area’’) vs.
forested portions of 10-km buffers around protected areas, rain-fed/intermediate inputs 6. Entire hotspots/wilderness areas (‘‘larger area’’)
vs. forested portions of hotspots/wilderness areas, rain-fed, and irrigated/high inputs. 7. Entire hotspots/wilderness areas (‘‘larger area’’) vs.
forested portions of protected areas, rain-fed, and irrigated/high inputs. 8. Entire hotspots/wilderness areas (‘‘larger area’’) vs. forested
portions of 10-km buffers around protected areas, rain-fed, and irrigated/high inputs. 9. Forested portions of hotspots/wilderness areas
(‘‘larger area’’) vs. forested portions of protected areas, rain-fed and irrigated/high inputs. 10. Forested portions of hotspots/wilderness areas
(‘‘larger area’’) vs. forested portions of 10-km buffers around protected areas, rain-fed and irrigated/high inputs.
will complement pressure for timber harvests in both regions—
regions where pressure for economic growth is considerable.
Although the remaining habitat in the Amazon and Congo
tropical wilderness areas provide remarkable opportunities for
conservation, concerted planning in these areas will be essential
to accommodate conservation amid rural sector development
associated with the agricultural expansion certain to occur.
In closing this discussion of results, it is important to
acknowledge limitations of this evaluation of agricultural
suitability. Despite its contributions to our understanding of
global agricultural potential and how it varies over geographic
space, the GAEZ project relied on data whose accuracy varied in
different parts of the world (28). Moreover, the GAEZ
assessment did not consider land degradation, an issue with
growing implications for agricultural productivity (11, 12),
although degradation data would further reduce agricultural
suitability. Although the GAEZ assessment included a broad
range of crops and crop categories, because of certain complicating factors in evaluating their productivity, it did not evaluate
suitability for certain perennial crops (e.g. grapes) and tree crops
(e.g. coffee), which are extremely important in some of the
biodiversity regions examined in this study. Finally, the results of
this study are limited by the 5 0 resolution of the GAEZ evaluation
and, as a consequence, certainly miss some of the variability of
agricultural suitability apparent at finer scales. Although useful
for assessing agricultural suitability for entire biodiversity
regions, such coarser resolution data are of lesser utility as
attention focuses on smaller geographic areas. Despite these data
limitations, remarkably consistent results and confirmation of
suitability assessments for selected localities based on personal
and expert experience suggest that our analysis accurately
measures the agricultural suitability of high biodiversity regions.
DISCUSSION
The results of this study indicate that in forested parts of the
most biodiversity-rich regions in the world, maintaining natural
habitat does not usually come at the expense of high agricultural production. Although conservation unquestionably constrains agricultural expansion, for most forested portions of
hotspots and tropical wilderness areas this constraint restricts
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crop production on land with low productivity potential. Notice
that this conclusion considers both absolute measures of
agricultural suitability and the suitability of forested protected
areas and buffers compared with that of the biodiversity regions
that contain them. The latter addresses the question of relative
impacts—the possibility that the agricultural suitability of land,
however poor, is still greater than that characterizing the
general geographic setting. In the majority of crop-geographic
entity–cropping scenario combinations examined in this study,
forested portions of biodiversity regions are less suitable for
agriculture than the entire regions, forested protected areas are
less suitable than both entire biodiversity regions and the
forested portions of biodiversity regions that contain them, and
forested 10-km buffers similarly are less productive than both
entire biodiversity regions and the forested portions of biodiversity regions where they occur.
Generally low agricultural suitability of forested areas
provides an opportunity to coordinate conservation and
development planning. Although we acknowledge the need for
more detailed local analyses before specific decisions are made,
the results of this study suggest that it should be possible to plan
for conservation and agricultural development such that the
two do not conflict. This is possible precisely because most of
the land valuable for conservation has low suitability for crop
production. When comparing agricultural suitability of forested
portions of biodiversity regions with entire regions, and
comparing suitability of forested portions of protected areas
and 10-km buffers around those protected areas with entire
regions, solutions become more challenging. Although forested
portions of biodiversity regions tend to be less productive than
the regions as a whole, several of the comparisons summarized
in Figure 4 show forested ecosystems as comparatively more
productive (although increased suitability is often small). In
such instances, consideration of forest benefits at different
scales for different stakeholders may make the conservation of
these areas attractive. Moreover, providing appropriate information to key decision makers may help to resolve such
problems, such as exchanging less agriculturally productive land
near protected areas for more productive land of less
conservation value elsewhere. Although land-use decisions are
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subject to existing land tenure, when questions of productivity
are important, as they often are in subsistence and commercial
agriculture, such exchanges may appeal to all involved.
In the few biodiversity regions with comparatively higher
agricultural suitability, strategic decisions can guide agricultural
development toward localities with the greatest potential for
agricultural yield that are not within or near protected areas. Such
decisions also may involve investment in roads and strategic use
of agricultural intensification, recognizing that the accompanying increase in yields due to the latter compromise conservation
efforts in some cases (43, 44). Lost agricultural yields from not
developing productive land in or near protected areas could be
offset in part by improvements in ecological services that would
have been used for sustained crop production (33, 45). Such
difficult decisions ultimately may require financial compensation
for not developing rich agricultural land of high conservation
importance, particularly in settings where such development is
essential to improving poor human conditions.
The results of this study show that conserving biodiversity in
forested ecosystems generally has not come—and need not
come—at the expense of important opportunities for agricultural development. When planning additional conservation
actions, such as establishing protected areas or corridors
between them, it is possible in most high biodiversity regions
to avoid land valued for its cropping potential, with agricultural
suitability evaluated both in absolute and relative terms.
Unfortunately, many existing protected areas already occur
near agricultural (7) or other activities (46–48), at a minimum
placing them in danger of isolation as islands of biodiversity
with declining utility for conservation (49). For biodiversity
regions with higher productivity in their forested portions—the
Amazon, Brazilian Cerrado, Congo, Eastern Arc and Coastal
Forests, and West African Forests—conservation success will
require careful attention in rural land use planning. Ultimately,
assembling a network of protected areas that conserve remaining biodiversity will not be easy even in light of generally limited
agricultural potential: in most cases, resident biodiversity can
withstand only limited disruption of its forest home, particularly in the tropics (50). Increased understanding of the
challenge of conservation in a world dominated by humans,
seeking possible solutions that benefit biodiversity as well as
efforts to improve the human condition, will help in the struggle
to save the earth’s biological heritage.
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51. First submitted 15 April 2004. Revised manuscript received 19 Aug. 2004. Accepted for
publication 19 Aug. 2004.
L. J. Gorenflo is a director in the Human Dimensions Program,
Center for Applied Biodiversity Science, Conservation International. His address: 1919 M Street, NW, Suite 600,
Washington, DC 20036 USA.
[email protected]
Katrina Brandon is a Senior Technical Advisor at the Human
Dimensions Program, Center for Applied Biodiversity Science,
Conservation International. Her address: 1919 M Street, NW,
Suite 600, Washington, DC 20036 USA.
[email protected]
Ó Royal Swedish Academy of Sciences 2005
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Ambio Vol. 34, No. 3, May 2005