When we humans tinker with an ecosystem’s composition and structure to suit our short-term economic desires, we risk losing species, either locally or totally, and so reduce, first, the ecosystem’s biodiversity, then its genetic diversity, and finally its functional diversity in ways we might not even imagine. With decreased diversity, we lose existing choices for manipulating our environment. This loss may directly affect our long-term economic viability because the lost biodiversity can so alter an ecosystem that it is rendered incapable of producing what we once valued it for or what we, or the next generation, could potentially value it for again. Maintaining backup systems is thus a critical link in the shared relationship between ecosystems and communities—social-environmental sustainability. With respect to humans tinkering with ecosystem processes, what might be the effect of overexploiting “bushmeat” on the self-reinforcing feedback loops and their backups that are so critical to the biophysical sustainability of tropical forests?
Plant-animal interactions and vegetative structure were studied in two geographically close tropical Bolivian forests, each of which experienced different intensities of hunting. It was hypothesized that a reduction of ground-dwelling mammals weighing 2.2 pounds or more in an “intensively hunted forest” would decrease the predation of seeds and the trampling of seedlings, as well as increase seedling survival and density, whereas an “occasionally hunted forest” (which held 1.7 times as many mammalian species as the intensively hunted forest) would have decreased tree-species diversity at the seedling stage in relation to the adult stage.
As predicted, predation on the seeds of the murumuru palm (which has edible nuts) was lower in the intensively hunted forest, and seedling survival was higher than in the occasionally hunted forest. But the intensively hunted forest displayed lower seedling densities and a higher ratio of seedling diversity to tree diversity than did the occasionally hunted forest.1 Reduction of collared peccaries from the intensively hunted forest may explain much of the between-site differences in seed predation, trampling, and seedling survival. Yet reductions of canopy-dwelling birds and mammals that disperse seeds, such as squirrels, monkeys, parrots, and macaws, can have a decidedly devastating effect on the diversity of plants and thus forest structure.
Hunting for bushmeat has profound negative effects on the species diversity, the standing biomass (the total weight or mass of living organisms in a defined area), and the size and structure of vertebrate assemblages in otherwise largely undisturbed Amazonian forests—and tropical forests in general. These effects are aggravated by forest fragmentation because fragments not only are more accessible to hunters but also allow, at best, a low rate of re-colonization from non-harvested refugia. Further, fragments, especially small ones, may provide a low quality of habitat and of resource base for the birds and mammals that eat fruits and seeds.
The size distribution of 5,564 fragments of topical forest—estimated from satellite images of six regions of southern and eastern Brazilian Amazonia—clearly shows that the tracts rarely exceed 25 acres. It thus seems patently obvious that persistent over-hunting in these areas is likely to decimate the populations of most midsized to large vertebrates not only from the fragments themselves but also from the fractured landscape. In particular, persistent hunting markedly reduces the number of large-bodied species greater than eleven pounds. This synergism has increasingly negative consequences for the life-sustaining feedback loops in Neotropical forests, which are dependent on interactive vertebrate assemblages with a full complement of avian and mammalian species. It is imperative, however, to account for long-lived individuals because they have low rates of reproduction and long generation times, which makes them more vulnerable to extinction than species with short-lived individuals, high rates of increase, and shorter generations.
HUMAN INTRUSION INTO THE FOREST
Twenty-three and a half million animals are killed annually in Amazonian forests for the bushmeat trade (an equivalent of 89,224 tons) with a market value of US $190.7 million, which is a conservative estimate. This number illustrates the enormous socio-economic value of bushmeat to the rural population of Brazilian Amazonia and highlights the staggering effect of hunters on vertebrate communities in tropical forests. Much of the illegal bushmeat hunting in Africa is clearly facilitated and intensified by the presence of logging concessions (large areas of land set aside for extracting timber), which are commonly backed by a loan from the African Development Bank in the Democratic Republic of Congo.
For example, in one such logging concession in the Sangha region of Congo, its geographic isolation, resulting transportation costs, and market demands forced commercial loggers to exploit only the most valuable timber. Here, the selective extraction destroyed an average of 6.8 percent of the canopy and thus, unlike clear-cutting, had far less impact on wildlife populations in and of itself. Nevertheless, line-transect surveys clearly showed that the abundance of primates was exceedingly low in the logged forest.
This outcome was not a direct consequence of thinning in the canopy, but rather was the result of extremely intensive market hunting, which coincides with surveying timber and the subsequent logging. Moreover, weapons and hunting camps were common, and vehicles belonging to the logging company were used daily to transport primates, duikers, and other animals. In addition, laws pertaining to wildlife in the Congo are openly violated and not enforced.
Whatever tropical forest one contemplates, the expansion of roads increases both human access and its accompanying hunting pressure. In the rainforests of southern Gabon, hunting had the greatest impact on duikers, forest buffalo, and red river hogs, which declined in abundance, and lesser effects on lowland gorillas and carnivores. In addition to hunting, the avoidance of roads further depressed the abundance of duikers, whereas sitatungas (swamp-dwelling antelopes, also called marshbucks) and forest elephants simply avoid roads. Although five species of monkeys showed little response to either roads or hunting, some rodents and pangolins (also known as scaly anteaters) increased in abundance, possibly in response to greater disturbance within the forest.
Roads had the greatest impacts on large and small ungulates, with the magnitude of road avoidance increasing with the increased pressure of local hunting. Nevertheless, even moderate hunting pressure can markedly alter the structure of mammal communities in central Africa and thus their ability of perform the ecological services that provided tropical forests with their complex, self-sustaining feedback loops.
Because oil companies have large tracts of land set aside for exploration and production (also termed concessions), wherein they accommodate human access by constructing roads and pipelines, these set-asides are often relatively safe areas for illegal hunting. For example, a bushmeat-trade monitoring program was established in the town of Gamba to assess the human pressure exerted on wildlife by the number of people attracted by the oil industry in the Gamba Protected Areas Complex.
The Gamba Protected Areas Complex is a 6,835-square-mile preserve on the southwest coast of Gabon, Africa, which not only supports significant habitat and species diversity but also has the country’s largest reserves of onshore oil. The complex, which is a designated series of connected faunal reserves and hunting areas, was established in the 1950s to protect areas of exceptionally rich wildlife diversity. Today, two national parks frame the Gamba complex: to the east is Moukalaba-Doudou, a 2,796-square-mile area of mountains rich in biodiversity (a refugia and great apes) and to the west is Loango (963 square miles), which is known for its terrestrial-marine megafauna, intricate habitat mosaics, and potential for ecotourism.
THE ILLEGAL KILL
During 279 days of observations in Gamba, 19 species of mammals, 4 species of bird, and 7 species of reptiles were tallied in a total of 2,845 animal carcasses with an estimated weight of 418,279 pounds. Despite the fact that the bushmeat trade is illegal in protected areas, the numbers of animals killed annually make it clear the bushmeat trade is not sustainable. The town of Gamba had the highest ratio of bushmeat to population in the country.
Non-sustainable hunting of bushmeat is often a more immediate and significant threat to the biological diversity in tropical forests than deforestation. To more fully understand the impact of the trade, the rate of exploitation of 57 species of mammals from the Amazon Basin and 31 species of mammals from the Congo Basin were compared. Estimates were compiled from anthropological studies that reported animals killed and brought into settlements in the regions, along with the average number of animals consumed per person per year.
The rates at which species with specific body masses were exploited was significantly greater in the Congo than in the Amazon. Thus, mammals of the Congo Basin must annually produce approximately 93% of their body mass to balance current losses to hunting, whereas Amazonian mammals must produce only 4% of their body mass. It is estimated that over 5 million tons of meat from wild mammals 0.15 million people annually in the Neotropical forest and 4.9 million people in the Afrotropical forest. However, the estimates for the Congo Basin are 4 times higher than those previously calculated for the region, a finding that leads to the conclusion that the current rate at which bushmeat is extracted from the African rainforests is more destructive than previously thought. Here, one might inquire why people eat bushmeat.
THE BUSHMEAT TRADE
Some people may eat it because they can afford it, but others choose it because it is a familiar and traditional source of meat that supplements a short supply from animal husbandry, confers prestige, tastes good, or simply adds variety. A 2002–2003 survey was conducted in 1,208 rural and urban households in Gabon in an attempt to understand the effect wealth and price had on the purchase of bushmeat.
Consumption of bushmeat, fish, chicken, and livestock was linked to increasing household wealth, but as the price of these commodities rose, consumption declined. Although the prices of substitutes did not significantly influence the selection of bushmeat, as the price of wildlife went up and its purchase fell, the acceptance of fish improved; fish and bushmeat thus appear to be dietary substitutes.
Now the question becomes: How does so much bushmeat get to the consumers in the first place? Little is known about the organizational dynamics of the trade or of the actors involved in it, and this lack of knowledge impedes the development of effective policies through which to protect the ecological services these wonderfully complex forests offer to all generations.
To rectify this lack, an investigation was launched into the structure and operation of a bushmeat-commodity chain that supplies a typical urban market—the city of Takoradi in southwestern Ghana, West Africa. Data collected from January through February 2000 uncovered 2,430 bushmeat transactions, which involved 17 species from 70 actors who traded along the commodity chain: commercial hunters, farmer hunters, wholesalers, market traders, and chopbar (cafe) owners. Although bushmeat was freely traded among these people, the primary route for terrestrial mammals was from commercial hunters through wholesalers to chopbars. In contrast, only farmer hunters, market traders, and chopbars were involved in the trade of invertebrates.
Wholesalers captured the largest per capita share of the market because each wholesaler handled 4% of all sales, whereas the chopbars were the top vendors because, as a group, they made 85% of all bushmeat sales to the public. Variation in the price of bushmeat is explained largely by the cost of transport and the preferences of consumers. Transport costs were most significant for hunters and, as one would expect, were greatest on long journeys that involved large loads. Nevertheless, the hunters obtained the greatest income per pound of bushmeat sold.
THE BUSHMEAT TRADE AND THE MILITARY
This type of simple commodity exchange does not, however, explain the whole bushmeat trade. To explore the complicated interlinkages of the informal bushmeat economy in times both of political stability and of armed conflict, a study of the trade was undertaken in Garamba National Park, Democratic Republic of Congo. The investigation focused on the sale of protected and unprotected species in urban and rural markets, with special emphasis on the commodity chains that supplied the markets.
During peacetime, protected species (predominantly elephants and buffalos) were poached in the park. Automatic weapons were required to hunt these large mammals, weapons supplied to hunters by the military officers who controlled the urban trade. During wartime, however, the military officers fled, leaving behind an open-access system, which encouraged a massive exploitation of protected species. Consequently, the sales of protected species increased fivefold in the urban markets.
In contrast, traditional chiefs, who administered the village markets, discouraged the use of such weapons. Therefore, rural markets remained relatively stable because of the continued authority of the village chiefs, which indicates that sociopolitical factors can be important in controlling the processes that drive species extraction. In addition, traditional authorities can be potentially valuable partners in protecting the ecological sustainability of African forests.2
THE POTENIAL “BUSHMEAT ENDANGERMENT” OF A NEWLY DESCRIBED SPECIES OF MONKEY
In a recent article (September 12, 2012), John A. Hart and others described a new species of monkey known locally as “lesula” was found in 2007 in the forests of the middle Lomami Basin in central Democratic Republic of Congo. The monkey’s geographical distribution is restricted to the lowland rainforests of central Democratic Republic of Congo between the middle Lomami River and the upper Tshuapa River. The team recommend the common name, “lesula,” for this new species, as it is the vernacular name used over most of its known range.3
Hart calls the lesula, which has a blond mane and bright-red patch on its lower back, a “gorgeous” animal Male lesulas can weigh up to 15 pounds, twice that of female lesulas. Males also have bright blue buttocks, which stand out in the dark, dense rain forest they roam.
Researchers hope the discovery of the lesula will lead to its protection. While it is not considered an endangered species, Hart says it is vulnerable because of the high demand for bush meat in the relatively small area it inhabits.4
As grim as the bushmeat trade may sound, we humans are continually changing the landscape in which we live—in that we have no choice. The ways in which we change the landscape, however, depend on the level of our consciousness of the effects we cause when our thoughts are translated into decisions, which are in turn converted into actions. There is a caveat, however: whereas nature is governed by impartial, biophysical principles, people are stirred by their desires and sense of values, which are always biased through cultural perceptions. Nevertheless, both nature and humans cause far-reaching effects in time and space through their actions. And, once we act, the outcomes—both short term and long term—are forever out of our control, whether we like it or not, admit it or not, or even understand it.
1. The preceding discussion of plant-animal interactions is based on Alejandra I. Roldán and Javier A. Simonetti. Plant-Mammal Interactions in Tropical Bolivian Forests with Different Hunting Pressures. Conservation Biology 15 (2001):617–623.
2. The preceding discussion of bushmeat is based on: (1) David S. Wilkie, John G. Sidle, and Georges C. Boundzanga. Mechanized Logging, Market Hunting, and a Bank Loan in Congo. Conservation Biology 6 (1992):570–580; (2) Emmanuel de Merode and Guy Cowlishaw. Species Protection, the Changing Informal Economy, and the Politics of Access to the Bushmeat Trade in the Democratic Republic of Congo. Conservation Biology 20 (2006):1262–1271; (3) Guy Cowlishaw, Samantha Mendelson, and J. Marcus Rowcliffe. Structure and Operation of a Bushmeat Commodity Chain in Southwestern Ghana. Conservation Biology 19 (2005):139–149; (4) Richard E. Bodmer, John F. Eisenberg, and Kent H. Redford. Hunting and the Likelihood of Extinction of Amazonian Mammals. Conservation Biology 11 (1997):460–466; (5) Carlos A. Peres. Effects of Subsistence Hunting on Vertebrate Community Structure in Amazonian Forests. Conservation Biology 14 (2000):240–253; (6) Roldán and Simonetti. Plant-Mammal Interactions in Tropical Bolivian Forests with Different Hunting Pressures. Conservation Biology 15 (2001):617-623; (7) Carlos A. Peres. Synergistic Effects of Subsistence Hunting and Habitat Fragmentation on Amazonian Forest Vertebrates. Conservation Biology 15 (2001):1490–1505; (8) John E. Fa, Carlos A. Peres, and Jessica Meeuwig. Bushmeat Exploitation in Tropical Forests: An Intercontinental Comparison. Conservation Biology 16 (2002):232–237; (9) Marc Thibault and Sonia Blaney. The Oil Industry as an Underlying Factor in the Bushmeat Crisis in Central Africa. Conservation Biology 17 (2003):1807–1813; (10) David S. Wilkie, Malcolm Starkey, Kate Abernethy, and others. Role of Prices and Wealth in Consumer Demand for Bushmeat in Gabon, Central Africa. Conservation Biology 19 (2005):268–274; (11) William F. Laurance, Barbara M. Croes, Landry Tchignoumba, and others. Impacts of Roads and Hunting on Central African Rainforest Mammals. Conservation Biology 20 (2006):1251–1261; (12) A. Alonso, M. E. Lee, P. Campbell, and others, eds. Gamba, Gabon: Biodiversity of an Equatorial African Rainforest. Bulletin of the Biological Society of Washington 12 (2006):1–448; (13) Smithsonian Institution, Gabon Biodiversity Program Briefing Paper 7 (2006):1–32.
3. John A. Hart, Kate M. Detwiler, Christopher C. Gilbert, and others. Lesula: A New Species of Cercopithecus Monkey Endemic to the Democratic Republic of Congo and Implications for Conservation of Congo’s Central Basin. PLoS ONE 7 (9):e44271. doi:10.1371/journal.pone.0044271.
4. Bazi Kanani. (September 13, 2012) ‘Gorgeous’ New Monkey Discovered in Africa. http://abcnews.go.com/blogs/headlines/2012/09/gorgeous-new-monkey-discovered-in-africa/
Text © by Chris Maser 2012. All rights reserved.
Excerpted in large part from my book, Earth in Our Care: Ecology, Economy, and Sustainability. Rutgers University Press, New Brunswick, NJ. (2009) 304 pp.
If you want more information about this book or want to purchase it, visit “BOOKS” on my website.