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Biodiversity in the cacao agroecosystem: shade management and landscape considerations

Biodiversity in the Cacao Agroecosystem: Shade
Management and Landscape Considerations
Russell Greenberg
Smithsonian Migratory Bird Center
National Zoological Park
Washington, D.C. 20008
Shade crops, such as cacao, provide habitat for plants and animals normally dependent upon tropical forest. This
enhancement of biodiversity in the agricultural landscape occurs primarily on a local scale — providing homes and food for
more generalized forest species that are intolerant of pastures or farm fields. Cacao plantations may also play a largely
undocumented role in protecting biodiversity at a global scale, when it is cultivated in regions of high endemism suffering
from heavy deforestation.
The ability of cacao farms to harbor biological diversity — particularly forest dependent species -- is known for only a few
taxa (primarily ants and birds) and from a few sites. Much of what we suspect to be true of cacao farms with respect to
biodiversity is based on research in similar systems (primarily coffee) or is inferred from established ecological principles.
On this basis, we suggest that 1) overall biological diversity and the diversity of forest dwelling organisms is higher in
cacao plantations than non-shade crops or pastoral systems; 2) diversity will increase with an increase in both floristic and
structural diversity of the shade level; 3) diversity within cacao plantations will be highest when they are located adjacent
to extant patches, corridors, or large tracts of forest. Shaded plantations may play a particularly critical conservation role
for migratory organisms (birds and perhaps insects) that arrive seasonally from the Temperate Zone, or from drier or
higher altitude zones.
Beyond any general concerns for protecting biodiversity, motivation for farmers to manage cacao holdings to optimize
biodiversity are two-fold. First, consumers are increasingly conscious of environmental impacts of their favorite
commodities. Since cacao historically has been grown in a biodiversity friendly manner, it may be possible to increase
chocolate sales in the rapidly growing "green" or environmental market. Second, within the high levels "unplanned"
biodiversity of traditional cacao farms, it is likely we will find many species that perform as unyet studied or quantified
"ecological services" such as biological control of pests and disease.
For a program designed to promote traditional shade approaches to cacao cultivation we recommend the following
The firm empirical establishment of the value of traditional cacao as a conservation tool. The geographic and
taxonomic scope of biodiversity surveys needs to be greatly expanded and conducted in a systematically
comparative fashion — comparing cacao farms to other agricultural habitats, comparing among different
management schemes of cacao, with the emphasis on the ability of cacao to harbor forest-dependent flora
and fauna.
A realistic assessment of the long term stability of populations of forest trees and other organisms (birds,
epiphytes, fungi) in traditional cacao plantations.
An evaluation of the selection of shade tree species and the mode of shade management to optimize farm
productivity and biological diversity. Research would include a detailed region by region assessment of the
use of shade trees by forest organisms of selected major taxa overlaid on information garnered on the
silvicultural and agronomic properties of the same tree species, as well as the use and value of tree
A comprehensive testing of the concept that the greater unplanned diversity of traditional farms will dampen
the population outbreaks of pest and disease organisms and improve pollination levels.
The development of a full range of incentives for farmers to grow cacao in a biodiversity friendly manner
including fair-trade practices, access to pre-harvest credit, carbon sequestration credits, avitourism, and
environmental funds based on taxing agrochemical inputs.
If traditional cacao is actively promoted and does not continue to be simply the result of laissez-faire neglect, then a
major research and extension effort will be required. Such a research program, ultimately aimed at improving the long
term stability of cacao production, needs to be based on the explicit assumption that traditional cacao plantations are
modified forest ecosystems. Because traditional cacao is a modified forest and not a field crop the research needs to be
based on both the holistic understanding of the cacao forest ecosystem alongside of more traditional agronomic
approaches. It remains to be seen how comfortably the ecological and agronomic approaches to cacao production can
Last year, the interest of tropical conservationists became riveted — albeit briefly
to the discovery of the Pink-legged Graveteiro (Acrobatornis fonsecai), a new species and genus of bird, in the cacao
plantations of Bahia (Pacheco et al. 1996). The occurrence of this uncommon forest endemic in Brazilian cacao, along with
the already well-known, yet endangered Golden-headed Lion Tamarin (Leontopithecus chrysomelas; Alves 1990)
underscores the role that such plantations might play in the protection of biodiversity. And even before this new bird was
described, conservationists concerned with the conservation of migratory bird in the increasingly deforested tropical
countryside had identified the promotion of cacao cultivation on forest-like farms as distinctly positive step (Petit et al
In the face of alarming rates of tropical deforestation, the cultivation of crops under the canopy of diverse shade trees
offers a glimmer of hope for the conservation of otherwise doomed biological diversity. Cacao, which evolved as an
understory or subcanopy tree of Amazonian forests, is one such crop plant that has traditionally been cultivated under a
modified forest or planted shade canopy. The continued cultivation of cacao under a diverse shade canopy will probably
enhance, at least on the local level, biodiversity in the tropical agricultural landscape.
However, the continued cultivation of cacao in a relatively biodiversity-friendly manner is by no means assured. In many
areas, large tracts of cacao have been converted to low diversity shade or even full sun systems. Meanwhile, small-scale
farmers employing the most traditional technologies are struggling to survive low and fluctuating prices and the constant
threat of disease and pests. An important question is how much shaded cacao farms can be altered in attempts to improve
yields and still maintain the environmental benefits of the traditional systems.
In the face of these economic threats with their day-to-day impact on the well being of millions of farm families, a case
has to be made for biodiversity being an important factor in a farmer's decisions concerning plantation management.
Outside of the value that farm communities might place on biological diversity, we suggest four factors that might provide
incentive for continuing to manage traditional cacao farms to optimize the diversity of forest flora and fauna: 1) an
outward appeal to the growing market for products with low environmental impact; 2) the short-term and long-term
ecological services — pollination, protection from pests and diseases, reduction in need for chemical fertilizers etc. — that
come from managing for biological diversity; 3) economic value that comes from products of the shade canopy plants; and
4) policies or programs that provide non-market incentives that might compensate for any productivity loss to farmers
experience by using the traditional shade management techniques.
Before the cocoa growing world embraces the concept of biodiversity friendly coffee anew, a stronger empirical basis for
this management approach needs to be established. As a first step towards establishing this basis — in this paper we
briefly assess what is well established and what needs further investigation with respect to three critical questions: 1) How
well do shaded cacao farms protect biological diversity, particularly species of forest dependent organisms? 2) How does
the management of cacao farmland influence levels of biological diversity; and 3) What is the value of biological diversity
associated with shade to the production of cacao as a sustainable crop.
A brief overview of the diversity of shade management systems in cacao
Shade component of cacao farms varies from natural forest canopy, to a small number of planted and uniformly trimmed
shade species, to largely non-existent — where any required shade is provided by the cacao tree itself (Wood and Lass
1985). Whatever the shade management system, we would argue that shade is more than just another farm attribute, but
rather, shade is a central characteristic of farms reflecting the biological and socioeconomic setting of cacao production.
Shade management is also strongly related to the degree of agrochemical usage, as well. The following is a brief overview
of the shade gradient of cacao farms (Fig. 1).
Rustic Cacao Management
Rustic cacao management, widespread in the humid portion of West Africa and local in northern Latin America (southern
Mexico to Brazil and Peru), is characterized by the planting of cacao under thinned primary or older secondary forest. The
resulting habitat is in many ways similar to degraded tropical forest in its floral and faunal composition. This is particularly
true at the canopy level, where untrimmed epiphytes, mistletoes and lianas support many other organisms.
Planted Shade Systems: Traditional, Commercial, and Specialized Shade
The planted shade system can range from having multiple species of planted shade trees with occasional remnant forest
species (traditional polycultural), to commercial shade where other crop trees are interspersed amongst planted shade
trees and the cacao, to monocultural, specialized where the shade is dominated by one or a few tree species or genus.
Some indigenous shade systems are truly diverse agroforests. However in most planted systems where a multitude of
shade species is found (up to 30-40 in some planted systems) — generally one or a few species comprise the "backbone"
shade in which other fruiting and timber species are inserted. Such backbone species, usually fast growing, nitrogen-fixing
legumes, include Erythrina spp., Gliricidia sepium, Cassia spp., Inga spp.
In some areas, cacao is grown under or intercropped primarily with fruit trees.
Technified Cacao Systems without Shade
Cacao cultivation without shade is common in Malaysia and becoming more widespread in parts of Colombia and Perú. It
is also common to cultivate young cacao under a sparse shade of banana. Although no studies have evaluated biodiversity
within these "sun" systems, it is likely that they provide little benefit to biodiversity conservation.
Abandoned Cacao Plantations
As a result of political instability, disease problems and low prices cacao farms are sometimes abandoned where cocoa may
sometimes be harvested but all serious farm management ceases. Because the cacao farm gradually reverts to secondary
forest, with the asociated forest faunal and flora, abandoned cacao may be particularly valuable for biodiversity
conservation. Such a pattern of succession is probably more common for diverse shaded systems that are close to forest
or forest patches (see Heinen 1992 for study of reptiles and amphibians).
Biodiversity in Cacao Plantations — The Concepts
Focusing the spotlight on the role of cacao plantations in the protection of tropical diversity reveals a promising avenue of
research and management. But the current assessment of this diversity is based in a weak scientific edifice. Published
research is taxonomically, geographically, and thematically scattered. In our attempts to briefly review what is known, we
will emphasize some of the organizing concepts of biodiversity research (Table 1) and then place the extant literature into
this framework (Table 2).
Relevant Comparisons
Scattered through the cacao research literature are studies of the numbers of species in various taxa found in particular
farms or farming regions. However, because studies have no comparative focus, they often are of limited utility in
addressing the core question of how well cacao protects biological diversity and how this protective role varies with
different management strategies. Important comparative paradigms in such studies are 1) how do cacao farms compare in
diversity and faunal and floral composition to alternative agricultural land uses; 2) how do cacao farms compare in these
parameters to comparable natural forest; and 3) how do cacao farms with different management systems compare with
each other.
Regional versus Global Diversity
The enhancement of regional diversity through protection of tropical forest organism in a particular area may or may not
make a significant contribution towards the conservation of global diversity by protecting extinction-prone species
depending upon the degree that those organisms survive and prosper in plantations, the amount of locally extant natural
forest in the area, and the overall degree of faunal and floral endemism in the region. For example, cacao farms may play
a more important conservation role in deforested Andean valleys and the Atlantic forests of eastern Brazil than in a heavily
forested portion of the Amazon Basin proper.
Planned Versus Unplanned Diversity
The term biological diversity may conger up divergent images to people with different training and interests. Agronomists
may think primarily about the diversity that, through planting or selective clearing, the farmer intends to be present in the
farm. To a large degree the diversity of the shade trees themselves is often the intended result of farm management. This
aspect of diversity is termed "planned diversity". The thousands of other species, from microbes to monkeys, that visit
or reside on the farm compose the
"unplanned diversity".
Parameters of Diversity and "Conservation Value"
The simplest parameter to examine is species richness (or species diversity which incorporates information on species-
abundance patterns). Although species lists are the most readily available statistic, it may be the most misleading and
difficult to interpret.
First, a habitat may have a long species lists - most of which involves generalist species or species that adapt easily to
human disturbance. In the case of cacao, we should examine any list to determine the degree to which species sensitive to
tropical deforestation can occur in cacao farms. So probably a better indicator of the conservation value of cacao farms
would be the forest species richness.
Species richness and forest species richness are much less straightforward measures than they seem. Unlike abundance
estimates, which become more precise with sampling effort, species richness generally increases and it is difficult to
extrapolate between two qualitatively or quantitatively different censusing efforts. Species richness can be compared for
equivalent efforts or the curves of the species numbers that accumulates with effort or area sampled can be examined.
Other more sophisticated estimation procedures (rarefaction) are available. The important consideration is that the survey
work needs to be based on a standardized and repeatable protocol. Another key issue when considering raw species
numbers is that the biological significance of a habitat is hard to evaluate simply on the basis of a species presence or
absence, particularly for mobile organisms where individuals wander out of typical habitat from time to time (Remsen
1994). It is useful to think of core species richness to biota — those that either reproduce or occur regularly and
predictably in a habitat. Ultimately we wish to know the long-term fate of forest species that reside in cacao plantations,
what we might think of as the sustained diversity.
Scale: the micro and macro of tropical diversity
Although studies of diversity on cacao farms tend to focus at the level of the farm and farm management, the basis for
diversity of any habitat needs to be addressed at various levels of scale. On the micro-scale, tropical forest ecosystems —
of which a shaded cacao farm is a highly modified form — consists of a large number of microhabitats, each of which
supports a high diversity of specialized organisms. In addition, many organisms depend upon these microhabitats for a
critical stage in their life cycle. Management that removes or modifies any of these microhabitats can potentially cause
critical changes in overall diversity. Consider the "aerial leaf litter" — an example from my own research on Neotropical
lowland forests. A number of birds specialize in foraging from leaves of canopy trees that hang in understory shrubs and
vines. If one collects arthropods from these leaves, the collection reveals a community of arthropods that live only, or
primarily in this microhabitat as well. Many other arthropods — particularly Orthopterans — rely upon these leaves as
diurnal hiding places. Manipulation of understory to remove lianas or dense vegetation will impact this microhabitat and
overall diversity in, as yet unknown ways. The same argument can be made for epiphytic plants, various forms of dead
wood, etc.
On the macro-scale, the size and configuration of a habitat patch and its spatial distribution with respect to existing forest
(and the size and configuration of that habitat as well) exerts tremendous influence on the diversity of the target patch. It
is likely that a number of forest organisms can occur in cacao, but require forest for part of their life cycle. In many areas,
cacao is grown on tiny parcels mixed in with many other crop types, rather than as contiguous bands of habitat, making it
difficult to conduct standard censuses on vertebrates and other taxa with large home ranges.
Seasonality and Phenology
Seasonality is a central issue in the study of most terrestrial habitats — including those located in the humid tropics. Most
tropical areas experience a seasonal rhythm in rainfall and those closer to the poles receive weather systems from higher
latitudes. This seasonality drives phenological peaks and valleys of leaf flush, flower and fruit production and variation in
humidity and soil moisture. Diversity must be assessed throughout the phenological cycles for species with limited activity
periods and mobile species (such as nectarivorous birds) that visit plantations in particular seasons. Few studies of cacao
have explicitly addressed this issue (but see Gibbs and Leston 1970).
Focal Taxa
Although we bandy about the term "biological diversity," most studies, in fact, have a taxonomic focus or set of foci.
Ecologists are becoming increasingly concerned with the concept of indicator taxa. That is simply to say that the response
of most disturbance sensitive organism may or may not be extrapolated from data gathered from birds, trees, or whatever
happens to be the taxonomic specialty of the investigator. We are grateful for even the sparing literature, so it is hard to
second-guess the particular taxonomic focus. On the other hand, as future studies are planned - some time should be
invested in selecting representative and important taxa. Criteria for selecting taxa of study include:
Well-known and well-loved taxa: Birds are a prime example of taxa that is disproportionately the focus of
research on biological diversity. In the case of cacao this has two advantages. First, birds ecology and
distribution is relatively well known and the census techniques established so that data on birds can be
evaluated and placed into a broader ecological context. Second, birds are well known and loved by the
chocolate-eating public and hence information about birds may prove useful interesting consumers in
issues of biodiversity in cocoa production.
Taxa most likely to fail: certain groups of animals are, because of their behavior and demography, more
extinction-prone than others. Focus on these taxa would provide information on the limits of cacao
plantations as a conservation tool.
Taxa most likely to succeed: Cacao plantations may be particularly important for the conservation of certain
taxa with ecological requirements satisfied by small patches of highly modified forest habitat. These taxa
would include such groups as bromeliads, sedentary arthropods, and amphibians, where populations can
persist in preserved canopy environments of limited extent. Long distance migratory birds is a another
group where the forest-dependent species are capable of persisting in relatively small and disturbed forest
Indicator taxa: a research program on biodiversity may select taxa that are representative of the more
complete spectrum of biodiversity. Such a selection should focus on taxa for which the systematic is
reasonably well known and taxonomic specialists are available.
Taxa with specific functional significance: an ecological guild is composed of species that perform a similar
ecological function. Such guilds can be based on growth form or trophic relationships or shared dispersal
and pollination characteristics. Research that strives to integrate the study of biodiversity and the
functioning of the cacao ecosystem should be focused on all taxa that constitute a guild and priority would
be set by functional importance. For example, herbivorous arthropods are consumed by birds, bats, lizards,
ants, and spiders and parasitized by a number of arthropod groups. Ultimately the diversity of all of these
groups should be examined to evaluate the role of unplanned biodiversity in the population dynamics of
pest or potential pest insects. However certain groups — such as ants (which make up 10-33% of
arthropod biomes of cocoa farms, Majer 1994) and spiders (Robinson and Robinson 1974) because of their
abundance, and birds and bats because of their size and high energy demands — would have greater
intrinsic functional significance and be a higher priority for research. Add to these, the parasitic and
hyperparasitic Hymenoptera that by virtue of their diversity and specialization may play a key role in
maintain populations of potential pests in check.
Keystone taxa: Certain groups of organisms are central to the maintenance of diversity of many other
groups. In particular, trees, shrubs and epiphytes provide homes and food for many other taxa that require
diversity in these groups to support ecological specializations.
Some Results of Research on Biodiversity in Cacao Farms
1. Trees and shrubs are thinned to 10% of their original abundance and lianas eliminated in the cabruca system of Bahia
(Aves 1990 for this section). Because of this, plant diversity is substantially reduced and modified by human management.
More importantly, regeneration is eliminated and eventually the naturally occurring trees are replaced by those planted.
Among mammals, large-bodied terrestrial mammals and larger primates were among the groups underrepresented in the
cacao. Cacao plantation bird assemblages lack many of the specialized understory species and supported low abundances
of foliage insectivorous birds and high relative high abundances of canopy frugivores and omnivores.
2. The Smithsonian Migratory Bird Center has been surveying the composition and diversity of birds in both natural and
anthropogenic systems in Southeastern Mexico for the past decade. We have worked in cacao plantations in two distinct
landscapes using very different farm management strategies. The first are small rustic plantations in the buffer zone of the
Montes Azules Biosphere Reserve in the Selva Lacandona of eastern Chiapas. The second is the planted shade of the more
extensive cacao zone of the lowlands of Tabasco on the southern Gulf Coast of Mexico. The species richness of the Selva
Lacandona cacao plantation (142 species in 20 transect survey weeks) was most similar to forest or disturbed forest
habitats (118-149) and considerably lower than pasture/open agricultural habitats (20 - 100 species). A high proportion of
the common species — both resident and migratory -- were shared with undisturbed tropical forest (36 forest breeding
species) The planted shade farms of Tabasco supported a considerably lower numbers of bird species than rustic cacao (84
species found in 220 point census a comparable census effort to the above transect data) — with virtually no forest
breeding species (5 species of vanishingly low abundances). Migratory species fare better than ecologically similar
residents. Some forest-dependent migratory species — such as Wood Thrush, Kentucky Warbler, male Hooded Warbler
and American Redstart were common. These results with migatory birds support the conclusions of a ground-level mist-
netting study of cacao grown under Erythrina in Belize (Robbins et al. 1992). In this study, the cacao had the most similar
migrant assemblage to natural forest of several crop types. In the Mexican study, we cannot easily tease apart to
landscape and management effects, but we can present the information on the avifauna of these systems as best and
worst case scenarios for the value of cacao in tropical forest bird conservation.
3. A small amount of data (Alves 1990 Parrish and Reitsma unpubl.), supports the concept that cacao grown close to
natural forest — particularly large tracts of forest — support a greater diversity of forest birds and mammals than those
that are isolated from natural habitats. Young (1994) has made a similar argument for invertebrates — including some of
the pollinators for cacao. In fact, the endemic vertebrates mentioned in the introduction (furnariid and tamarin) seem also
require forest patches and can only use cacao as a secondary habitat (Alves 1994, Pacheco et al. 1996).
4. The ant assemblages of cacao farms comprise a complex three dimensional mosaic of dominant territorial species each
with a distinct set of associated subordinate species (Room 1971, Leston 1973, Majer 1993, 1994). This pattern of
community organization is similar to that found in natural forest (where it has been compared). There is some suggestion
that in plantations of structurally simple shade, fewer ants are able to more thoroughly dominate the habitat.
5. Bats, non-volant mammals and birds were compared between isolated rustic cacao plantation, other agricultural
habitats (shaded and non-shaded) and forest patches in Las Tuxtlas, Veracruz, Mexico (Estrada et al. 1993a, 1993b, 1994,
1997). Cacao supported high abundances and relatively high numbers of species in these different groups. For some taxa,
cacao supported the second highest species richness — behind natural forest fragments. Overall, plantations had higher
diversity where they were closer to natural forest patches.
The importance of specific microhabitats (mistletoe, epiphytes etc.) has been underscored by research of Room (1971,
1972) and Young (1994 and ref. therein).
6. We were able to locate few systematic survey of biodiversity comparing cacao plantations and forest or other habitats
in Africa or Asia. Room (1975) compared terrestrial ant assemblages across habitats in Papua, New Guinea and reported
that cacao and rubber plantations most closely approached forest in species richness. Room noted that the high diversity
in the tree plantations is comprised of early and late successional species. Room (1973) speculated that the above-ground
ant diversity of Ghanaian cocoa farms was substantially greater than those of New Guinea, because the former are small
rustic plantations and the latter larger planted shade farms. Leston (1970) cites several studies suggesting high diversity
insects in cacao plantation including Lepidoptera (174 species in Ghanaian plantations) and Coleoptera (56 genera of
beetles in West African), also noting that the high diversity results from a mixture of species characteristic of forest and
open farmland. Room (1971) found an ant fauna in the cocoa farms of Ghana that approached natural forest in its
diversity. T. Smith (pers. comm.) has a large database from mist-netting birds in plantations of Cameroon and notes that
the diversity and abundance of forest birds is relatively high. Latinos and Smith (1992) found that although some endemic
species occurred in cacao plantations of Book and Cameroon, the most common species in the former site were
characteristic of disturbed habitats.
The most striking feature of the published research so far is its paucity. Systematic studies of otherwise well-studied taxa
are all but lacking from Africa and Asia (regions of origin of over 80% of the world's cocoa). Some quantitative and a fair
amount of qualitative information supports that idea that rustic cacao supports a modified forest flora and fauna —
combining forest and open country species. A very small amount of data — and a lot of common sense -- suggests that
planted systems using a few species of dominant shade tree support far less diversity than rustic systems. However, the
comparative study of different management systems is wide-open fields for future research. Furthermore, outside of a few
studies primarily on invertebrates, the evaluation of the contribution of specific microhabitats and tree species has not
been accomplished. These are the sorts of studies that will be most useful for making concrete recommendations on the
effect of shade management on biodiversity.
Lessons from the coffee ecosystem
Insights into the management of Cacao plantations need not be restricted to the sparse information garnered from cacao
plantations. Other shade grown crops, particularly coffee, share many of the same management patterns and are often
times simply replacement habitats on an elevation gradient. Interpreted with some caution, the somewhat greater volume
of research on the effects of different shade management systems in coffee should be consulted in designing research and
management for cacao. Based on a review research on biodiversity and shade management of coffee (mainly Perfecto et
al. 1996), we can garner the following insights — which have been used to develop specific field criteria for ecologically
sustainable coffee:
Diverse shade coffee plantations support a relatively high diversity of birds, mammals, reptiles, insects,
epiphytes etc. In part, this diversity is a unique combination of early succesional and forest species.
However, shade plantations, to varying degrees, do protect forest species.
Bird diversity, epiphyte diversity and presumable the diversity of other groups and the relative
representation of forest species increases with the increased vertical stratification of arboreal vegetation. In
particular, the presence of even a small number of tall trees (>15 m) greatly increased diversity.
Planted (Inga spp.) and rustic plantations of similar stature supported similar levels of avian diversity — but
the rustic had a higher proportion of specialized forest species.
Diversity of frugivores and nectarivores increases with the diversity of flowering and fruiting trees —
vertebrates that do particularly well include hummingbirds, tanagers, and fruit and flower feeding bats.
Plantations may be important to migratory organisms (both long distance and altitudinal) by providing a
habitat with an abundance of fruit and flowers in the canopy during the tropical dry season.
Greater floristic diversity provides more diverse and seasonally available floral and fruit resources. In this
regard, trees with long or year round fruiting and flowering (such as Ficus) maybe particularly important.
Shade trees with perennial foliage supports greater bird abundance and diversity, particularly during the
critical dry season months.
The presence of dead and rotting wood in trees and on the ground contributes considerably to diversity,
particularly invertebrates.
The presence of parasitic plants (mistletoes) and epiphytes contributes substantially to diversity by
providing shelter, nest sites, flower and fruit resources.
Terrestrial arthropods — particularly ants — are much more diverse in the presence of shade, presumably
due to climatic buffering and the presence of leaf litter.
Large bodied vertebrates and species dependent upon viny vegetation and undisturbed understory do no
persist well in even rustic plantations.
Parasitic and hyperparasitic Hymenoptera retain a disproportionately high level of diversity in shaded versus
monocultural coffee plantations.
The presence of weedy and shrubby areas contributes substantially to avian diversity and presumably to the
diversity of other groups as well.
Plantations located closer to extant forest support a high diversity of forest birds than more isolated
The Value of Biological Diversity in the Production of Cacao
Up to this point we have been discussing ways in which cacao farms can promote biological diversity. To what degree can
we argue that managing for biological diversity in general and specific types of organisms in particular can enhance the
functioning of a cacao farm? It is fashionable to call such relationships between the natural world and our own economic
interests "ecological services". If we can be allowed a bit of characterization, we would like to contrast three views of
how to treat ecological services or more generally the role of nature itself in the production of crops:
Replace nature. Certainly a dominant viewpoint of the latter part of this century, ecosystem functions —
such as the regulation of populations of pest and disease organisms — are replaced by human
technological approaches.
Selective use of nature. The viewpoint underpinning Integrated Pest Management, the natural system is
studied and particular biological control agents introduced or encouraged to control specific problems.
Holistic ecological (organic) management of nature. Management of ecosystem so that trophic structure and
mutualistic relationships are kept as intact (similar to natural forest) as possible — resorting to specific
control strategies as a last resort. The pests and pestilence would come indirectly through the management
of vegetation.
The following is a cogent description of a more holistic ecological view of disease control:
"Many of the pods of cacao forest were stained with the handiwork of Monilia and Phytophthora diseases. Abandoned cacao
plantations are reservoirs for fungal organisms that attack cacao pods. In the pristine rainforest, the fungi would just be a
small part of a complex balancing act imposed by networks of specialized predator-prey associations, which dampen the
tendency for most species to proliferate. But vast monocultures of cacao are sitting ducks for sweeping infestations of such
organisms." (Young 1994:136).
We believe that more emphasis should be placed on the third view of nature on cacao farms. It should also be noted that
the holistic ecological view is philosophically similar to the underpinnings of the organic agriculture movement. However,
the concept that the cacao ecosystem should be managed for biological diversity should not be based simply on some
philosophical love of nature but on evidence garnered from scientific research. Here we discuss several areas of promising
Probably the best worked-out example of indirect effects of ecosystem-level management on cacao production is in the
area of pollinator diversity. The work of Young (1994) and others suggest that the natural pollinators (Ceratopogonid
midges) require microhabitats for breeding — including rotting cacao fruit -- that are often removed from highly-managed
Cacao plantations. Pollination may actually be highest when cacao is grown adjacent to natural forest vegetation.
Pest Control
Probably the most obvious ecological service provided to the cacao farms is the possible biological regulation of pest or
potential pest insects. The general hypothesis that we put forth is that populations of organisms are less likely to reach
pest or epidemic proportions in the presence of high levels of biological diversity. Rather than manipulate specific predator-
prey or other relationship, the manipulation of the cacao habitat to retain the coevolved ecological relationships
characteristic of natural forest is the first approach to be taken to prevent disease or pest problems. Although natural
predators, such as the Black Cocoa Ant (Dolichoderus thoracicus) of Southeast Asia, are often used in specific Biological
Control programs (Khoo and Ho 1992), it has also been suggested that the natural "ant mosaic" is generally effective at
reducing pest problems (Room 1971, Leston 1973, Majer 1994). Outside of the work on ant mosaics there seems to have
been little research conducted on the interaction between the assemblage of natural predators and symbionts with pests
and disease organisms — real or potential.
Most studies of the impact of natural predators on arthropods in agroecosystems have focused on the control of particular
pest species (Kirk ET al., 1997). For cacao, major pests would include Cocoa Pod Borer (Conopomorpha cramerella),
Mealybugs (Planococcus spp.), Mirids, and the Cocoa Beetle (Steirastoma breve) and each region has a host of minor pest
as well. Minor pests reach epidemic population levels much less often than do the major pests. Controlling pest insects has
been the focus for research on predator- insect interaction in forest ecosystems. However, recent work on the impact of
bird predation on the herbivorous insect community as a whole has suggested that birds play an important role in
preventing non-outbreak populations and species from substantially reducing the growth rate of forest trees ( Marquis and
Whelan 1994). Furthermore, predators — including not just birds, but bats, spiders, ants, parasitic wasps and many other
groups -- may be much more important than previously thought in preventing species from achieving pest status to begin
with. If a diverse web of predators does confer stability on herbivore populations, then some management issues become
important. Several authorities have suggested that the removal of shade and the spraying of insecticides are two major
contributing factors in the development of pest species (Leston 1970, Wood and Lass 1985). Shade removal has been
shown to have a direct impact on capsids, but the presence of canopy vegetation may have an indirect effect as well. Both
shade removal and application of chemicals probably reduce the abundance and diversity of potential predators and
parasitoids and provide prima facie evidence supporting the ecological view of population regulation. In many ways, the
management of biodiversity through shade management is analogous to the use of natural buffer vegetation for field and
orchard crops (see Altieria and Letourneau 1982).
Nutrient Cycling and Disease Control
The impact shade on leaf litter and soil components of the cacao agroecosystem provides some exciting possibilities. The
leaf litter and the climatic protection of the shade trees create an environment that may support a greater diversity of
natural predators as well. McVean (1992) has suggested that natural predators of nematodes, which damage plant roots,
is housed in the leaf litter created by shade trees in coffee farms. Of course, the diversity of soil and litter organisms is
critical in nutrient breakdown and cycling. In particular, fungal symbionts such as vesicular-arbuscular micorrhizae (VAM)
play a key role in the nutrient budget of moist forest understory plants (Janos 1980) and cacao has long been known to
harbor such fungae ( Laycock 1945). Micorrhizae and endophytic fungi may play an unrecognized role in conferring disease
resistance (Herre pers. comm.), certainly a central issue for economically sustainable cacao production. Factors that effect
fungal and microbial diversity are poorly known. The study of the role of these naturally occurring organism can take the
more focused approach, searching for specific species or groups of species that effect particular disease organisms, and at
the same time a more holistic ecological approach of examining how the entire community functions and in what ways we
can manage the system to maintain the original forest-like diversity.
Research and Management Recommendations.
An assessment of what is known and not known concerning shade management and biodiversity of cacao farms is
presented in Table 1. The following are major recommendations that follow from this analysis:
(assuming that natural or "unplanned" biodiversity needs to be optimized)
Use structurally and taxonomically diverse shade of native species.
Leave buffer zones along streams and property boundaries of native vegetation.
Leave epiphytes, lianas and parasitic plants in shade tree canopies.
Retain standing dead wood.
Weed in a manner to protect some forest tree regeneration.
Encourage shade cacao farms as a buffer zone crop adjacent to forest reserves.
Form corridors of habitat — particularly on mountain slopes — consisting of forest patches, cacao farms
(lower elevation) and coffee farms (higher elevation).
Encourage cacao farming with native forest trees in regions lacking protected forest. Development of a full
range of incentives for farmers to grow cacao in a biodiversity friendly manner including fair-trade
practices, access to pre-harvest credit, carbon sequestration credits, avitourism, and environmental funds
based on taxing agrochemical inputs.
Establish of the value of traditional cacao as a conservation tool. The geographic and taxonomic scope of
biodiversity surveys needs to be greatly expanded and conducted in a systematically comparative fashion
— comparing cacao farms to other agricultural habitats, comparing among different management schemes
of cacao, with the emphasis on the ability of cacao to harbor forest-dependent flora and fauna.
Assess of the long-term stability of populations of forest trees and other organisms (birds, epiphytes, and
fungi) in traditional cacao plantations.
Evaluate the selection of shade tree species and the mode of shade management to optimize farm
productivity and biological diversity. Research would include a detailed region by region assessment of the
use of shade trees by forest organisms of selected major taxa overlaid on information garnered on the
silvicultural and agronomic properties of the same tree species, as well as the use and value of tree
Continue to test the concept that the greater unplanned diversity of traditional farms will dampen the
population outbreaks of pest and disease organisms and improve pollination levels.
Altieri, M. A., Letourneau, D. K. Vegetation diversity and insect pest outbreaks. CRC Critical Reviews in Plant Sciences
Alves, M. C. 1990. The role of cocoa plantations in the conservation of the Atlantic forests of southern Bahia, Brazil. M. S.
thesis. Univ. of Florida. Gainseville, Florida.
Estrada, A., R. Coates-Estrada and D. Merritt, Jr. 1993. Bat species richness and abundance in tropical rain forest
garments and in agricultural habitats at Las Tuxtlas, Mexico. Ecography 16:309-318.
Estrada, A., R. Coates-Estrada, and D. Meritt Jr. 1994. Non flying mammals and landscape changes in the tropical rain
forest region of Los Tuxtlas, Mexico. Ecography 17: 229-241.
Estrada, A., R. Coates-Estrada, and D. A. Merritt., Jr. 1997. Anthropogenic landscape changes and avian diversity at Los
Tuxtlas, Mexico. Biodiversity and Conservation 6: 19-43.
Estrada, A., R. Coates-Estrada, D. Meritt Jr., S. Montiel, and D. Curiel. 1993. Pattern of frugivore species richness and
abundance in forest islands and in agricultural habitats at Los Tuxtlas, Mexico. In: T.H. Fleming and A. Estrada (eds.):
Frugivores and Seed Dispersal: ecological and evolutionary aspects. Kluwer Academic Publ. Dordretch, The Netherlands,
pp. 245-257.
Gibbs, D.G. and D. Leston. 1970. Insect phenology in a forest cocoa-farm locality in West Africa. Journal of Applied
Ecology 7: 519-548.
Greenberg, R., P. Bichier, A Cruz, etc. MS. The impact of bird insectivory on herbivorous arthropods and leaf damage in
some Guatemalan coffee plantations.
Greenberg, R., J. Salgado, I. Warkentin, and P. Bichier. 1995. Managed forest patches and the conservation of migratory
birds in Chiapas, Mexico. In: Conservation of Neotropical Migratory Birds in Mexico, Symposium - Workshop Proceedings.
Wilson, M.H. and S.A. Sader, eds.. Maine Agricultural and Forest Experiment Station Misc. Publication 727. pp. 178 - 189.
Heinen, J.T. 1992. Comparisons of the leaf litter herpetofauna in abandoned cacao plantations and primary rain forest in
Costa Rica: Some implications for faunal restoration. Biotropica 24(3): 431-439.
Janos, D. P. 1980. Vesicular-arbuscular mycorrhizae affect lowland tropical rain forest plant growth. Ecology 61: 151-162.
Khoo, K. C. 1192. The influence of Dolichoderus thoracicus (Hymenoptera: Formicidae) on losses due to Helopeltis theivora
(Heteroptera: Miridae), black pod disease, and mammalian pests of cocoa in Malaysia. Bull. Entom. Res. 82:485-491.
Kirk, D. A., M. D. Evenden, Pierre Mineau. 1997. Past and current attempts to evaluate the role of birds as predators of
insect pests in temperate agriculture. Current Ornithology 13, 175-269.
Larison, B. and T. B. Smith. 1996. A survey of montane and lowland birds from three sites on the island of Bioko,
Equatorial Guinea. Report to the government of Equatorial Guinea.
Laycock, D. H. 1945. Preliminary investigations into the functions of the endotrophic mycorrhiza of Theobroma cacao L.
Tropical Agriculture, Trinidad 22:77-80.
Leston, D. 1970. Entomology of the cocoa farm. Annual Review of Entomology 273-294.
Leston, D. 1973. The ant-mosaic-tropical tree crops and the limiting of pests and diseases. Pest Articles and News
Summaries 19, 311-341.
MacVean, C. 1992. Causas y naturaleza del mal de viñas en cafetos de Guatemala. Publ. Instituto de Investigaciones,
Universidad de Guatemala.
Majer, J. D. 1993. Comparison of the arboreal ant mosaic in Ghana, Brazil, Papua New Guinea and Australia -- its structure
and influence on arthropod diversity. Pp. 115-141 in J. LaSalle and I. Gould (Eds.). Hymenoptera and biodiversity. CAB
International. Wallingford,
Majer, J. D. 1994. Arboreal ant community patterns in Brazilian cocoa farms. Biotropica 26:73-83.
Marquis, R. J., Whelan, C. J. 1994. Insectivorous birds increase growth of white oaks through consumption of leaf-chewing
insects. Ecology 75, 2007-2014.
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Table 1. Recommendation Matrix for Shade Management and Shade Management Research
Bird Diversity and Overall Biodiversity
1. We know — based mostly on studies of coffee —that for a number of taxonomic
groups, diversity increases with the presence of shade trees. The proportion of forest or
woodland species also increases with the presence of a shade canopy. The reason for these
increases is the presence of new habitat structures, as well as the amelioration of
microclimate and the presence of more, different food sources to support greater diversity
at low trophic levels (which in turn supports greater diversity at higher trophic levels). In
birds and ants, low structural diversity many allow few aggressive species to dominate.
2. We suspect that the diversity and composition of the associated flora and fauna
increases in predictable ways with increases in the structural and floristic diversity of the
plantations and (up to a point) with total canopy cover.
3. It is possible that increased complexity of trophic and other ecological relationships
dampens the occurrence of pathogen or pest outbreaks.
I. Presence of Shade
4. We recommend that in order to support higher levels of biological diversity, cocoa be
grown under a shade canopy. We further recommend that this canopy be as floristically
diverse as practical. Research is required in different regions to establish the relationship
between shade levels and tree composition to the diversity of some selected taxa (i.e.,
epiphytic plants, Lepidoptera, birds) that represent different levels of vagility, forest
dependence etc. We further recommend that the efficacy of natural predation and disease
resistance on pests and pathogens be studied under different shade regimes.
II. Forest (Rustic)
Shade Canopy
1. We know from studies of both coffee and cocoa that a shade management system with
thinned forest trees resembles a degraded form of natural forest, with a higher level of
diversity of birds, trees, epiphytes etc. than any other shade management system.
2. We suspect, based on some narrower studies, that (1) is also true for cacao. We
further suspect that a canopy of thinned primary forest supports more of the local forest
specialist species than managed secondary forest.
3. We do not know the influence of different levels and strategies of tree thinning on
diversity. Further, there have been no studies of the long-term equilibrium diversity under
different landscapes and cacao plantation size (assuming there is an equilibrium). Because
of poor reproduction (due in part to weeding in the case of trees) species populations may
not be self-replacing. We do not know under what circumstances the management of forest
for cacao is the ultimate cause of habitat degradation or is an alternative to destruction.
4. We recommend that cocoa be grown under managed natural forest whenever feasible.
However, we do not recommend that new large tracts of forest be managed for cocoa
production until further study - on a region by region basis - of how cocoa growing impacts
forest protection. We recommend long-term and experimental studies on the stability of
rustic cocoa farms as ecological systems.
III. Floristic
Diversity of
1. We know that based on few empirical studies and ecological principles, there is a
positive relationship between the diversity of shade trees and bird diversity. We suspect
that many groups will show enhanced diversity as well.
2. We suspect that this is partly due to increased structural diversity, diversity of
chemical defenses, and reduction of phenological gaps In leaf, fruit and flower production.
We suspect that dominant shade trees that are native, perennial, and with heavy foliage
cover support greater bird diversity, as well as greater diversity in most other taxonomic
3. We do not know what mix of common shade trees, such as Inga, Erithryna and other
trees optimizes cacao production and biological diversity.
4. We recommend that cocoa be planted under as taxonomically diverse a canopy as
possible. We advocate the establishment of a program of interdisciplinary research on the
degree to which particular trees support biological diversity throughout the year along with
the ease with which the trees are propagated and the degree to which the tree competes
with or provides refuge for pathogens and pests of cocoa.
Diversity of
Shade Tree
1. We know, based on studies in coffee and ecological principle, that the greater the
foliage height diversity (presence of plant canopies at different strata) the higher the
overall diversity for birds and most other taxonomic groups. Further, the higher absolute
amount of foliage at all levels the greater the amount of refuge of prey from predators. We
know that the greater abundance (and diversity?) of epiphytic and parasitic plants, as well
as liana the greater the diversity of birds.
2. We suspect that the greater the number of tall trees, even at lower overall levels of
canopy cover, the greater the bird diversity as well as the representation of a number of
forest taxa. We suspect that the greater the abundance of standing dead wood, the greater
the diversity of arthropods, birds and many other taxonomic groups.
3. We know little about the specific relationship between shade tree composition and the
abundance and diversity of secondary structures (epiphytes etc.).
4. We recommend that shade trees and secondary trees be selected, in part, to maximize
structural diversity. We further suggest that trimming be done in such a way as to allow a
portion of the shade trees to reach natural heights and that minimal pruning of epiphytes
and parasitic plants on shade trees be carried out. We suggest that interdisciplinary
research with agronomists and ecologists be conducted to determine what is an optimal
level of shade tree pruning.
V. Cacao Farms in the
1. We know that forest patches that are larger and closer to tracts of forest support a
greater diversity of forest forms than smaller and more isolated patches. We also know
that forest patches located along altitudinal gradients with intact habitat supports higher
diversity — particularly of mobile organisms than those in an area of uniform topography.
2. We suspect that shade plantations connected to forest by corridors of shade plantation,
forest, or riparian growth; will sustain higher levels of forest diversity and provide habitat
for mobile forms as well.
3. We do not know quantitative effects of surrounding landscape on the composition of
any shaded cacao system for any taxa.
4. We recommend that, wherever possible, cacao farms be clumped to form larger
habitat tracts. Cacao farms should be connected to remnant forest tracts through corridors
of habitat — ideally forest, but also other shaded plantation (coffee at higher elevations,
for example), and gallery vegetation. We recommend that the development of cacao as a
shade crop be institutionally linked to regional programs of forest protection.
... This is because indiscriminate use of pesticides kills natural predators/parasitoids in the process, preventing the natural control of the population growth of the insect pests. Research has also shown that populations of some insects are less likely to reach pest levels in the presence of high levels of insect diversity (Greenberg 1998). Pesticides not only cause outbreak of insect pests in cocoa agroforestry systems but impact on the health and life span of pollinators (Brittain et al. 2010). ...
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Ecological role of insects in cocoa agroforestry systems is a key component of biodiversity that generally underlines what insects do in cocoa agroforestry systems. Although insects are often under-appreciated and viewed by many cocoa farmers as a nuisance and pests, they provide a diversity of ecosystem services in cocoa agroforestry systems. Farm management practices affect the role and function of these insects, and consequently the ecosystem services and disservices they provide. This paper reviews the importance of insects in cocoa agroforestry systems and examines five major ecosystem service that insects provide. It also highlights farm management practices that affect ecosystem services and disservices provided by insects in cocoa agroforestry systems. The paper further summarizes some of the major and minor insect pest species that can be found in cocoa agroforestry systems, the damages they cause, as well as their management strategies. The conclusion provides insight on how to conserve valuable ecosystem services provided by insects in cocoa agroforestry systems, suggests innovative farm management practices to reduce disservices provided by some insect pest species, and offers recommendations for future research.
... Several research studies have shown that cocoa plantations have the capacity to conserve many animal species, possibly more than any other anthropogenic land-use system (Faria et al., 2007;Rice & Greenberg, 2000;Schroth & Harvey, 2007;van Bael et al., 2007). For example, in a study that surveyed an assemblage of migratory birds, the cocoa plantation had the most similar migrant assemblage to natural forest (Greenberg, 2004). Shaded cocoa agroforestry systems can also maintain beneficial ecosystem services and minimize potential ecosystem disservices through trophic and non-trophic interactions (Felicitas et al., 2018). ...
Cocoa is an important crop for Ghana's economy, contributing 25% of Gross Domestic Product (GDP). The crop, however, is mainly cultivated on forest‐derived soils and is a major cause of land‐use change. Termites are an important biological component of tropical ecosystems providing numerous ecosystem services. Previous studies have indicated that termites are sensitive to forest disturbance and decrease in richness and abundance across land‐use intensification gradients, with consequences for the essential services that they provide. Native shade trees are often used to improve cocoa cultivation and may reduce the detrimental effects of land‐use change on some aspects of biodiversity. The aim of this study was therefore to explore how termites respond to land‐use change along a shade‐tree gradient in Kakum National Park and surrounding cocoa farms in Ghana (from forest at 80% tree cover to cocoa with no shade cover, to the extreme of cultivated arable crop land). It was predicted that termite richness and abundance would decrease with decreasing shade cover, and with increasing distance from the forest edge. Thirty‐four species from 29 genera were sampled, with Ancistrotermes crucifer being found in all the locations (47% of all encounters). Species richness and abundance differed marginally across the land‐use gradient, as well as the distance from the forest edge; however, species richness did not show any significance with distance. All the same, termite communities were robust to the disturbance. Our findings suggest that though site influenced species richness and abundance, cocoa trees can play a crucial role in maintaining biodiversity and environmental quality in an agricultural landscape by providing a habitat for forest species that are not found in pastures or farm fields. However, we caution that the relatively low forest baseline of existing forest diversity may inflate the value of cocoa land, with those forests no longer representing undisturbed natural habitats: this highlights that shifting baselines may need to be accounted for when interpreting findings in the Anthropocene. Termites are an important biological component of tropical ecosystems providing numerous ecosystem services. Native shade trees are often used to improve cocoa cultivation and may reduce the detrimental effects of land‐use change on some aspects of biodiversity. Our findings suggest that though site influenced species richness and abundance, cocoa trees can play a crucial role in maintaining biodiversity and environmental quality in an agricultural landscape by providing a habitat for forest species that are not found in pastures or farm fields
... Because traditional cacao is a modified forest and not a field crop the research needs to be based on both the holistic understanding of the cacao forest ecosystem alongside with the more traditional agronomic approaches. It remains to be seen how comfortably the ecological and agronomic approaches to cacao production can coexist [9]. ...
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The presence of cacao industry plays a critical role in the economic development of a country. A study was conducted to determine the cost, return and added value along the value chain stages of cacao in Camarines Sur, Philippines. Sixty-eight farmers served as respondents using purposive sampling technique and interviews/key informant surveys were conducted. Results of the study showed that cacao production has high return on investment of 77.89% and 160% for the farmer and processor, respectively but a low return on investment of 13% for traders. The value added from farmer to processor is Php 590.00/kilogram, and Php 125.00/kilogram from processor to trader. Various opportunities and prospects for cacao production had been identified such as increased technical and production support from the government, presence of R & D programs, increasing trend towards wellness & healthy lifestyle, and increasing businesses offering cocoa-based products. Recommendations include improvement in access and availability of processing facilities, improvement of market information for farmers, provision of trainings to enhance capability of farmers, strengthening of farmers' groups to increase their access to technical and financial assistance from government and provision of infrastructure support and storage facilities.
... Shade is not the most valuable feature according to farmers. [22,23] resolved that soil evaporation decreases proportionally over the growing seasons as the ground surface is increasingly shaded by crops and shade plant canopy. These facts validated the significant effects of shade treatments on increased percentage survival of cacao on the field after transplanting. ...
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Cocoa agrosystems can provide available habitats for wildlife species, due to the structure and diversity of established shade trees in plantations. The objective of this research is to calculate the index of importance and forest value of shade trees used in cocoa agrosystems in the region of Comalcalco, Tabasco, Mexico. Field sampling was carried out to collect data on breast height diameter, canopy diameter and canopy height, these variables were used to estimate the importance value index and the forest value index. The trees with the best indexes of importance and forest value are Erythrina americana (IVI = 62.34 and FVI = 50.94), Bursera simaruba (IVI = 62.53 and FVI = 66.99) and Samanea saman (IVI = 56, 85 and FVI = 42.93). The dynamic of shade trees in cocoa agrosystems is important since it could be used as an input variable to evaluate and predict, through an ecological niche model, the quality of the available habitat for the conservation of wildlife such as birds, reptiles and arboreal mammals.
Due to the structure and diversity of established shade trees in plantations, cocoa agrosystems can provide available habitats for wildlife species. The objective of this research is to calculate and, describe the structure and composition of shade trees used in cocoa agrosystems in Comalcalco, Tabasco, Mexico. Field sampling was carried out to collect data on breast height diameter, canopy diameter, and canopy height, these variables were used to estimate the importance value index and the forest value index. The trees with the best indexes of importance and forest value are Erythrina americana (IVI = 62.34 and FVI = 50.94), Bursera simaruba (IVI = 62.53 and FVI = 66.99), and Samanea saman (IVI = 56, 85 and FVI = 42.93). The dynamic of shade trees in cocoa agrosystems is important since it could be used as an input variable to evaluate and predict, through an ecological niche model, the quality of the available habitat for the conservation of wildlife such as birds, reptiles, and arboreal mammals.
en The Guineo-Congolian “rain” forest (G-C forest) in West and Central Africa is threatened by deforestation. From 1975 to 2013, the extent of the G-C forest decreased by 37%, from about 131,000 to 83,000 km². Overall, 46% of bird species in the G-C forest (123 of 268) have declining populations, and about 31 species (12%) are categorized as endangered, near threatened, or vulnerable. Impacts of harvesting for “bushmeat” and the cage bird industry are largely unknown, but, of 60 species of birds in the G-C forest known to be hunted or trapped, six are categorized as vulnerable, one as near threatened, and one as endangered. In addition, 35 of the 60 species are estimated to have decreasing populations, 18 species have stable populations, and three are increasing in number. The impacts of clearing or disturbing G-C forest to cultivate cash crops are not fully known, except that avian diversity is markedly reduced in such areas. Traditional “sacred groves,” mostly small patches of forest, are not formally designated as conservation areas, but may serve as protected sites for some species of birds. Temperatures have increased and rainfall has decreased over the last five decades in West Africa. These changes will likely contribute to a further loss of suitable habitat for range-restricted species of birds. In addition, species currently found in lowland and montane habitats may be forced to move to higher elevations. Of 53 species of birds found in lowland habitat, five are endangered, seven are near threatened, 11 are vulnerable, and one is data deficient, suggesting that ~44% of lowland species may have an increased risk of extinction. Countries with G-C forest all have large human populations with high incidences of poverty, resources harvested at unsustainable rates, and increasing rates of deforestation. Networks of large protected areas in West and Central Africa, with much tighter controls over unsustainable harvesting, are urgently needed to ensure conservation of the birds and, more generally, the biodiversity of the G-C forest. RESUMEN es Una reseña del estatus de conservación de las aves del bosque guineo-congolés de África El bosque ‘lluvioso’ guineo-congolés (bosque G-C) en el occidente y centro de África está amenazado por la deforestación. De 1975 a 2013, la extensión del bosque G-C decreció 37%, de cerca de 131,000 a 83,000 km². En general, 46% de las especies de aves en el bosque G-C (123 de 268) tienen poblaciones en declive y cerca de 31 especies (12%) están caracterizadas como en peligro, casi amenazadas o vulnerables. Los impactos de la extracción de ‘carne de monte’ y la industria de aves de jaula son en su mayoría desconocidos, pero, de 60 especies de aves que se cazan o capturan en el bosque G-C, seis están categorizadas como vulnerables, una como casi amenazada y una como en peligro. Adicionalmente, se estima que 35 de las 60 especies tienen poblaciones en declive, 18 tienen poblaciones estables y tres están incrementando sus números. Los impactos del desmonte o perturbación del bosque G-C por cultivos comerciales no es del todo conocido, excepto que la diversidad de aves es marcadamente reducida en dichas áreas. Los ‘huertos sagrados’ tradicionales, en su mayoría pequeños parches de bosque, no están designados como áreas de conservación pero podrían servir como sitios protegidos para algunas especies de aves. En el occidente de África, las temperaturas se han incrementado y la precipitación ha decrecido. Estos cambios muy probablemente contribuirán a una mayor pérdida del hábitat apropiado para especies de aves de hábitats restringidos. Adicionalmente, las especies que actualmente se encuentran en hábitats de tierras bajas y montanos podrían ser forzadas a desplazarse a mayores elevaciones. De 53 especies de aves en hábitats de tierras bajas, cinco están en peligro, siete están casi amenazadas, 11 son vulnerables y una es deficiente en datos, lo que sugiere que ~44% de las especies de tierras bajas podrían tener un mayor riesgo de extinción. Todos los países con bosque G-C tienen grandes poblaciones humanas con altos índices de pobreza, recursos extraídos a tasas no-sostenibles y crecientes tasas de deforestación. Las redes de grandes áreas protegidas en África occidental y central, con controles mucho mayores sobre la extracción no-sostenible, se necesitan urgentemente para asegurar la conservación de las aves y, más ampliamente, la biodiversidad del bosque G-C.
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The highly diverse tropical forests are fast being depleted and converted into isolated fragments which endangers the existence of wild animals. These fragments are interconnected by human-dominated agroforestry systems. To conserve the wild animals it is important that such agroforestry systems have the potential habitat to support the survival of the enormous regional biota. The present study was carried out in agroforestry systems (agrisilviculture systems, home gardens and tea gardens) in Assam to understand their role in conservation of different biological groups (mammals, birds, butterflies, reptiles and frogs). Total visual count method was deployed in home gardens and agrisilviculture system and line transects were laid in tea gardens for recording the faunal diversity. Altogether, 364 animal species (consisting of 14 mammal species, 185 bird species, 133 butterfly species, 18 reptilian species and 14 amphibian species) were recorded from the selected study sites of agroforestry systems. The highest animal diversity was found in home garden (311 spp.), followed by tea garden (275 spp.) and agrisilviculture system (187 spp.). Out of the 364 species recorded, only 1.09% were threatened (endangered and vulnerable) species and 1.37% were near threatened species according to the IUCN Red List. Wild animal species richness was significantly and negatively associated with distance from forest and positively associated with fruiting and flowering vegetation. Thus, the agroforestry systems with their flowering and fruiting vegetation, though cannot substitute the forest habitat but can be useful in providing shelter to the generalist species and their populations.
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Cocoa is traditionally grown in agroforestry systems (AFS). It is essential to the household and regional economy and plays an important role in natural resource and environmental services conservation. In recent years, the vegetation structure and diversity of cocoa AFS throughout the world are being simplified as farmers consider that the removal of trees helps to increase yields and reduce disease incidence. However, debate exists on the relationship between tree shade and diversity and cocoa yields and the incidence of disease such as frosty pod rot, one of the most important fungal infections in cocoa cultivation. The objective of this study was to analyze changes in agroforestry structure, plant species diversity, uses, yields, the incidence of frosty pod rot disease in cocoa agroforestry systems, and discuss the consequences of the simplification of this particular AFS in the municipality of Acacoyagua, Chiapas, Mexico. Inventories were carried out in 27 plots. Interviews were applied to families to assess ecological, technical, and productive variables. Incidence of frosty pod rot disease and yields were estimated on-farm and through interviews over a period of 3 years. Multivariate cluster analysis, Pearson correlation analysis, the Levene test for equality of variances and a non-parametric U Mann–Whitney test were carried out. Three types of cocoa agroforests were identified as a result of a structure simplification: (1) traditional cocoa polyculture; (2) cocoa with Legumes Inga spp and Lonchocarpus spp.; and (3) cocoa with diverse, scattered, predominantly wild trees. Fifty species were recorded in shade vegetation, with a diversity index of 3.15. Simplification in tree structure did not have a significant effect on cocoa yield nor on the incidence of frosty pod rot disease. On the contrary, it resulted in a decrease in plant diversity and provisioning of food and other products. Farmers undertake few agricultural practices; some practices are eventually carried out, such as the pruning of cocoa trees and shade-trees, removal, and burial of diseased fruits, and weeding. Seven out of 27 plots sampled yielded more than 300 kg ha⁻¹, and one plot attained a yield of 437.5 kg ha⁻¹; however, yields averaged 155.8 kg ha⁻¹ and incidence of frosty pot rot averaged 9.6%, regardless of AFS type. These results highlight the importance of improving AFS management which in this case appears to be the most critical factor for attaining an increase in yields. Low levels of production and the incidence of frosty pod rot subsequently reduces farmers’ motivation to continue cultivating cocoa, placing the crop at risk and increasing the possibility of a change in the land-use.
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We here describe Acrobatornis fonsecai, a new genus and species in the Furnariidae, from the Atlantic Forest of southeastern Bahia, Brazil. Among the outstanding features of this small, arboreal form are: black-and-gray definitive plumage lacking any rufous; juvenal plumage markedly different from adult; stout, bright-pink legs and feet; and its acrobatic foraging behavior involving almost constant inverted hangs on foliage and scansorial creeping along the undersides of canopy limbs. Analysis of morphology, vocalizations, and behavior suggest to us a phylogenetic position close to Asthenes and Cranioleuca; in some respects, it appears close to the equally obscure Xenerpestes and Metopothrix. New data on the morphology, vocalizations, and behavior of several furnariids possibly related to Acrobatornis are presented in the context of intrafamilial relationships. We theorize that Acrobatornis could have colonized its current range during an ancient period of continental semiaridity that promoted the expansion of stick nesting prototypes from a southern, Chaco-Patagonian/Pantanal center, and today represents a relict that survived by adapting to build its stick- nest in the relatively dry, open, canopy of leguminaceous trees of the contemporary humid forest in southeastern Bahia. Another theory of origin places emphasis on the fact that the closest relatives of practically all (if not all) other birds syntopic with Acrobatornis are of primarily Amazonian distribution. Acrobatornis fonsecai has a most unusual distribution in a restricted region in which lowland Atlantic Forest has been converted virtually entirely to cocoa plantations. Until very recently a lucrative and vitally important source of income for Bahia, the economic base for cocoa production has suffered catastrophic, apparently irrecoverable, decline owing to 'witch's broom' disease, which has proven resistant to all forms of control. The predictable wave to cut find sell the tall trees shading failing cocoa plantations has already begun in earnest with the consequence that the remnant forest canopies in this region, upon which Acrobatornis fonsecai is totally dependent, are being rapidly destroyed. This remarkable new furnariid and the secrets it holds for elucidation of phylogeny, evolutionary history, speciation patterns, and zoogeography, if not safeguarded immediately, when its habitat is still for sale, could disappear in the coming decade.
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Comparisons among three forest stands at La Selva were made of biomass, abundance, richness, relative abundance, evenness and species overlap of herpetofauna collected in leaf litter plots. The forest stands were primary forest and two different cacao plantations abandoned for five and 25 yr. Abundance and biomass of herpetofauna were greater in more recently disturbed sites, but evenness, richness, and diversity were greater in less recently disturbed sites. The more recently disturbed sites also had deeper leaf litter, which may influence prey availability, and higher percent canopy open, which may lead to extremes in temperature and moisture availability, compared to undisturbed primary forest. Herpetofaunal restoration is thus a relatively slow process, and presence of primary forest is important for maintenance of some rare species. -from Author
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We examined the indirect effects of insectivorous birds on plant growth through consumption of leaf-chewing insects in a Missouri Ozark deciduous forest. Over a period of 2 yr, we compared insect numbers, leaf damage, and resultant plant growth for control saplings of white oak (Quercus alba), vs. saplings that we caged to limit access by insectivorous birds but not herbivorous insects. In a third treatment, we sprayed insecticide on young white oak trees to determine the impact of the insect herbivores on plant growth in the presence of birds. The total number of insects encountered on plants inside of cages was twice that on control plants for both years. Insecticide spray reduced herbivore numbers substantially but did not eliminate them. As a result of the treatments, cage plants suffered 25% leaf area loss, control plants 13%, and spray plants 6% at the end of the first season (34, 24, and 9%, respectively, for the 2nd yr). As a result of the differences in damage, cage plants produced one-third less total aboveground biomass compared to insecticide-treated plants, with control plants producing intermediate value. Differences in biomass production were due mainly to decreased leaf biomass, which in turn was associated with decreased leaf size in subsequent years as a result to high damage during the previous year. This is the first terrestrial ecosystem study to demonstrate a significant impact of insectivorous birds on plant growth. Our results suggest that over the long term observed declines in North American populations of insectivorous birds may reduce forest productivity because of potentially higher numbers of leaf-chewing insects and the concomitant negative effect on plant growth.
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Many bird species consume large quantities of invertebrates, some of which are considered agricultural pests. However, relatively few quantitative studies demonstrate that avian predators can reduce agricultural insect pests below a level at which unchecked populations would cause economic damage to crops or require treatment with pesticides. In fact, since the subject of economic ornithology (“all relations of birds that has any bearing upon the material welfare of [humans]”— McAtee, 1933) was last reviewed (e.g., McFarlane, 1976; Sweetman, 1958), there have been only a handful of published studies on the role of birds in agricultural ecosystems, and most of these refer to small-plot effects, with no attempt to aggregate the results at the level of an agricultural economic unit, i.e., the farm.
Sampling by light trap, insecticide knockdown and other methods has given data on seasonal population changes in many insects and a few spiders in an area of semideciduous high forest largely devoted to cocoa growing at Tafo, Ghana. Populations of most species showed seasonal change and in every month some species were in a period of major increase. There are several characteristic seasonal population curves which, when associated with botanic and climatic events, lead to the conclusion that six seasons should be recognized. These can be defined by a combination of mean rainfall (more or less than 4 in./month) and mean monthly sunshine (more or less than 5.5 h/day). The seasons, listed together with some of the events we have discussed, are: (1) Dry sunny. Maximum fruit production, abundance of fruit-feeding and seed-feeding insects, continuing into the following season. Species thought to be favoured by effects of drought and related stress factors on host-plant nutrition also increase. (2) First wet sunny. Maximum leaf production; abundance of leaf-feeding insects and their predators. Maximum breakdown of leaf litter; abundance of litter-feeding and fungus-feeding insects. (3) First wet dull. Decline in leaf feeders and their predators. Abundance of timberborers. (4) Dry dull. Biologically similar to wet dull seasons; forms with numbers closely correlated with rainfall, for example timber-borers, may decline. (5) Second wet dull. (6) Second wet sunny. Shorter than the first wet sunny season, but period of submaximum leaf production; abundance of leaf feeders and their predators. Species that depend for food on primary production of plant tissues in the form of leaves or fruits have maximum numbers in the three sunny seasons. Their populations appear to respond directly to seasonal changes in the amount of food.
In experiments with plants grown in pots, vesicular-arbuscular mycorrhizal increased seedling growth of 23 to 28 species from a lowland tropical rain forest region. Mycorrhizae improved survival in six species and cotyledon retention in five species. Mycorrhizae also increased the size of bacterial nodules and the proportion of nodulated plants among three leguminous species. Growth of seedlings lacking mycorrhizae slowed greatly or ceased after attainment of sizes correlated with average seed dry mass. Removing cotyledons from individuals of two species that are dependent on mycorrhizae, however, did not increase their response to inoculation. Thus, seed reserves are important for mycorrhiza formation as well as for seedling growth before infection. Large seeds are advantageous to plants that depend on vesicular-arbuscular mycorrhizae because they provide mineral reserves upon which the seedling can draw while awaiting infection. Seedlings of some species could not grow without mycorrhizae, but inoculation did not affect the growth of other species. Species that are least dependent on mycorrhizae have light seeds and colonize disturbed habitats.
(1) The mistletoe Tapinanthus bangwensis growing on cocoa in Ghana was considered as a microhabitat which could be subdivided into three obvious regions: the junction consisting of fused mistletoe haustorium and hypertrophied host tissues; the plant consisting of the mistletoe branches and leaves; and the air surrounding the mistletoe. The fauna of each subdivision was sampled, and it was found that though the number of species taken in any subdivision was very large, the number of regularly occurring species was very small. The most conspicuous group in the air around the mistletoe was the Diptera, which accounted for more than half the species taken. On the plant the Araneida contributed more than a quarter of all species taken, while in and on the junction the Araneida, Coleoptera and Hymenoptera each contributed about 20% of the species taken. (2) Consideration of only the most common species in each subdivision showed that on the plant, and in and on the junction, the ants and their associated Homoptera were by far the most important groups. In the air and around the plant, the Diptera were again numerically dominant. (3) Notes are presented on various aspects of the biology of groups of species considered to be of relatively great ecological importance in the mistletoe microhabitat, such as wood borers, ants and Homoptera. Further notes are given on some less important but otherwise interesting species such as a polymorphic snail and some ant mimics. (4) The paper forms a background to work on the organization of the recurrent mistletoe fauna which will appear in further papers.
(1) Forty-eight general and 128 species of ants are listed from various microhabitats in 250 m2 of a cocoa-farm locality in Ghana. (2) The ant faunas of the microhabitats are compared, and it is noted that the majority of the species nest in dead wood and forage in the litter. (3) Two broad categories of foraging microhabitat are recognized--exposed and cavity. (4) Three species of ant invaders into the forest zone from savannah were taken in the locality. (5) The relative distributions of species' foraging territories in insolated cocoa canopy were investigated. (6) The frequencies of sixty-seven species in 168 samples are given, and may be taken as a rough guide to the relative abundance of territories of these species. (7) The mechanisms underlying numerical dominance in cocoa-farm ants are discussed and some implications for the use of ants as biological control agents are suggested. (8) It was shown that the five common dominant ants of the microhabitat had significantly different numbers of subdominant ants associated with them. It is suggested that this reflects the relative specializations of those dominant ants. (9) Unmodified chi2 analysis of the data was found to give a meaningful grouping of species into communities. It is suggested, along very general lines, how these communities function and interact with those species not included in them. (10) The extremely close association between Oecophylla longinoda and Crematogaster castanea?, and its significance, are briefly discussed.