By NOMVUYO CHISUTA –

DIFFERENT patterns of anthropogenic forest disturbance can affect forest wildlife in both tropical and temperate regions in many ways.

The overall impact of different sources of structural and nonstructural disturbance may depend on: (1) the groups of organisms considered; (2) the evolutionary history of analogous forms of natural disturbance; and (3) whether forest ecosystems are left to recover over sufficiently long intervals following a disturbance event.

The wide range of human-induced disturbance events vary widely in intensity, duration and periodicity, and are often mediated by numerous economic activities, including timber and no timber resource extraction.

One of the most human enterprises that can severely affect wildlife is hunting. This may result in faunal assemblages drastically being disfigured in highly modified forest landscapes, compared to those in truly undisturbed forest lands containing a full complement of plant and animal species.

Hunting

Hunting is perhaps the most geographically widespread form of human disturbance in tropical forests, although the total extent of this form of non-timber resource extraction cannot be easily mapped using conventional remote-sensing techniques.

Effects of hunting are likely to be considerably aggravated by isolated forest fragmentation because fragments are more accessible to hunters, allow no (or very low rates of) recolonisation from non-harvested source populations, and may provide a lower-quality resource base for the frugivore–granivore vertebrate fauna.

Many parts of West Africa, South-east Asia, and the neotropics are becoming chronically overhunted, partly as a result of burgeoning human populations that often escape to and become marginalised in frontier regions.

Exploitation of wild meat (the meat from wild animals often referred to as bush meat) by tropical forest-dwellers has also increased due to changes in hunting technology, scarcity of alternative protein sources, and because it is often a preferred food.

Large-bodied game birds and mammals providing highly desirable meat packages and hunted for either subsistence or commercial purposes are particularly affected, because they are the main target species and tend to be associated with low reproductive rates, thus recovering slowly from persistent hunting pressure.

Subsistence Hunting

Subsistence game hunting can often have profound negative effects on the species diversity, standing biomass, and size structure of vertebrate assemblages in tropical forests that otherwise remain structurally undisturbed.

This occurs mainly through local population declines, if not extirpation, of large bodied vertebrate taxa which make a disproportionately large contribution to non hunted forests in terms of their aggregate biomass and role in ecosystem functioning.

Overharvested forest sites where large game species have been depleted thus tend to be dominated by small-bodied species that are either bypassed or ignored by hunters.

Regardless of the nature of density compensation by small bodied species following the local extinction of large vertebrates, important species interactions or ecosystem functions associated with large body size such as dispersal of large-seed plant species and herbivory of tree seedlings may no longer take place.

Overhunting

Overhunting of wildlife for meat consumption has reached an unprecedented scale across the humid tropics, causing local extinction of many vulnerable species.

Yet productivity of tropical forests for wild meat is at least an order of magnitude lower than that of tropical savannas, and can only support less than 1 person per square kilometer if they depend entirely on wild meat for their protein.

Reasons why the scale and spatial extent of hunting activities have increased so greatly in recent years include human population growth and migration; severe reduction in forest cover and non hunted source areas; increased access via logging roads and paved highways into remote forest areas allowing hunters to harvest wild meat for subsistence or cash; the use of efficient modern hunting technologies especially firearms and wire snares; and, in some regions, greatly increased trade in wild meat.

Forest defaunation driven by wild meat hunters has therefore become one of the most difficult challenges for tropical forest wildlife conservation.

In addition to drivers of the bush meat harvest, wildlife depletion in tropical forests can be driven by extractive activities targeted to other desirable animal parts or products, including skins, feathers, ivory, horns, bones, fat deposits, eggs and nestlings, as well as live-captures of juveniles or adults for aviaries, aquaria, and the pet trade.

These activities are often poorly regulated in the humid tropics, and have been responsible for wholesale extinctions of many target species.

Mitigation measures

Policy responses to the overexploitation of wildlife can be placed into two classes: (i) Demand-side restrictions on off take, to increase the cost of hunting, and (ii) the supply-side provisioning of substitutes to decrease the benefit of hunting.

Restrictions on off take vary from no-take areas, such as parks, to various partial limits, such as reducing the density of hunters via private property rights, and establishing quotas and bans on specific species, seasons, or hunting gear, like shotguns.

Where there are commercial markets for wildlife, restrictions can also be applied down the supply chain in the form of market fines or taxes.

Finally, some wildlife products are exported for use as medicines or decoration and can be subjected to trade bans under the aegis of the Convention on International Trade in Endangered Species (CITES).

Bioeconomic modeling of a game market in Ghana has suggested that imposing large fines on the commercial sale of wild meat should be sufficient to recover wildlife populations, even in the absence of forest patrols.

Fines reduce expected profits from sales, so hunters should shift from firearms to cheaper but less effective snares and consume more wildlife at home. The resulting loss of cash income should encourage households to reallocate labor toward other sources of cash, such as agriculture.

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