Climate change can also play a more or less direct role in the changing dynamics and ecology of diseases in natural systems. Multiple factors contribute to increased pathogen emergence, including rapid population growth of both people and livestock, the intensification of agriculture, encroachment into wildlife areas, increased exploitation of wildlife and natural resources, modification of landscapes and ecosystems and globalization.

As with any environmental change, inevitably there will be winners and losers. The winners are likely to be those species with greater phenotypic flexibility - greater capacity to respond to change- such as those that use multiple habitat types and perhaps display weaker migratory connectivity (individuals from one breeding population may migrate to one of many non-breeding areas and vice versa). Thus, common species are likely to become even more common, and scarce species scarcer, resulting in a general decline and change in biodiversity.

Loss and deterioration of habitat seem to be the most likely impacts of climate change on vertebrates. Migrants may be affected disproportionately because of their reliance on high latitude, high altitude and wetland habitats as well as on particular stopover sites, which are vulnerable not only to habitat loss, but also to a reduction in seasonality (especially at high latitudes/altitudes) as winter temperatures are increasing faster than those in summer.

Species with generalized and unspecialized habitat requirements are likely to be able to tolerate a greater level of climatic and ecosystem change than specialized species with their strict habitat or environmental requirements. However, many species rely on environmental triggers or cues for migration, breeding, egg laying, seed germination, hibernation, and spring emergence and a range of other essential processes. While some cues such as day length and lunar cycles will be unaffected by climate change, others such as rainfall and temperature (including their interacting and cumulative effects) will be heavily affected by climate change. Species become vulnerable to changes in the magnitude and timing of these cues when they lead to an uncoupling with resources, or essential ecological processes e.g., where early spring warming causes the emergence or movement of a species before their food sources are available. Species dependent on interactions that are susceptible to disruption by climate change are at risk of extinction, particularly if they are highly dependent on the particular resource species and cannot substitute other species.

Climate change might affect the intensity and frequency of human wildlife conflicts indirectly, by modifying environments and their productivity, and favouring some species that cause problems for humans. Together with increased human population densities, climate change is exacerbating existing conflict situations around the world. Changes in climate may indirectly affect bushmeat species by affecting people’s livelihoods (e.g., livestock, agricultural production) and therefore lead to increased reliance on bushmeat species for survival and coping strategies. Climate change will also be responsible for the increased frequency and severity of wildfires which may affect wildlife habitats to a point where displaced animals can no longer find food, compete for territory or access shelter.

Examples of defaunation are numerous across the world, yet the impacts of unsustainable hunting relatively to other drivers of forest change such as habitat alteration (i.e., land-use changes, destruction, fragmentation), and impact of invasive species, is less considered and very subtle, but nevertheless important in the long term. While hunters may not always deliberately destroy trees to obtain bushmeat, the depletion of hunted species can also have wider impacts on the forest community and, more indirectly, on carbon storage, forest nutrient cycling and forest regeneration.

Defaunation leads to changes in the composition of wildlife species. These changes might have important and sometimes irreversible impacts on forest dynamics if they translate into the loss of species that serve as pollinators (such as large fruit bats), seed predators (e.g., pigs, peccaries, agoutis, large squirrels) and seed dispersers (e.g., primates, frugivorous bats, frugivorous birds, forest ungulates), which indirectly play a role in carbon sequestration. Defaunation might unleash trophic cascades that derail ecological processes, resulting in changes in community composition and loss of diversity. ‘Keystone species’, ‘ecosystem engineers’, or organisms with high community importance value are species or groups whose loss has a disproportionately high impact on the ecosystem compared to the loss of other species. Local extinction of top predators can trigger large changes in prey populations, which in turn alter browsing or grazing to the point where large regime shifts or ecosystem collapse can result.

Elephants and other herbivores can play a major role in modifying vegetation structure and composition through their feeding habits (including differential herbivory and seed dispersal) and movements in the forest (killing a large number of small trees). Many ungulate species, such as wild pigs and duikers, are among the most active seed dispersers or predators; thus a significant change in their population densities will have a major effect on seedling survival and forest regeneration. In defaunated ecosystems, studies have found wide-ranging changes in plant physiology, recruitment, species composition, community changes, and declining tree species diversity.

0ver-hunting leading to defaunation is disadvantageous for plant species with seeds dispersed by animals, and therefore gives a comparative advantage to species with seeds dispersed by wind, like lianas (woody vines that climb into the tree canopy), which also store less carbon than trees per unit volume, and can kill trees. All of these processes occur to a greater or lesser degree in all types of forests, but are most important in humid tropical forests because of high species richness and very strong relationships between plants and animals. (See figure 1)

Figure 1. The inter-relations between climate change and wildlife overexploitation (source: Hinsley et al., 2014)

Bushmeat and REDD+

Originally proposed in 2005 as a way to use financial incentives to mitigate global climate change, Reducing Emissions from Deforestation and forest Degradation (REDD) has evolved to include conservation, sustainable management of forests and enhancement of forest carbon stocks, in what is now known as REDD+.

Biodiversity protection is still viewed principally as a co-benefit of the REDD+ process, with conservation of forest tree cover and carbon stocks providing the main measures of success. However, focusing solely on tree cover and carbon stocks does not protect other species or ecosystem services, which may be threatened by other factors, most notably by unsustainable and often illegal hunting. The Cancun safeguards on REDD+ now officially acknowledge that the benefits of REDD+ go well beyond emissions reductions to include forest conservation, sustainable economic development, and biodiversity preservation. At the project level, such safeguards are validated and verified by independent bodies, such as the Verified Carbon Standard (VCS) and the Climate, Community and Biodiversity Alliance (CCBA). Despite the definition of safeguards, most REDD+ initiatives on the ground do not specifically consider sustainable wildlife management (including management of wildlife threats) as a measure to improve carbon storage potential in the long term.

Successful examples where wildlife has been included in mitigation measures include the Kasigau Corridor REDD+ project that protects over 500,000 acres of forest and brings the benefits of direct carbon financing to Kenyan communities while also securing the entire wildlife migration corridor between Tsavo East and Tsavo West National Parks. However, the scope is more on wildlife protection than on the use of wildlife for bushmeat use.

Bushmeat and adaptation strategies

In traditional forest communities, many non-timber forest products (NTFPs), including bushmeat, are part of household subsistence strategies, providing macronutrients, carbohydrates, fats and proteins, or other essential micronutrients, such as various minerals. Hunting is part of the coping strategies when regular access to agricultural commodities is not possible (e.g., after extreme climatic events) or in cases where no agriculture is possible. In some cases, bushmeat may just provide exceptional ‘treats’ rather than essential nutrients, but these nevertheless may be important due to their cultural and economic impacts. Despite the need for climate change adaptation, some poor tropical regions highly dependent on bushmeat for local livelihoods (e.g., from the Congo Basin) have not yet fully integrated climate change strategies into existing sectoral frameworks.

In other countries (e.g., Mexico, Southern African countries), bushmeat and wildlife in general are now included in adaptation strategies in several ways: either in strategies related to land and water protection and management, direct species management, monitoring programs for wildlife and ecosystems, and strategies related to law and policy, including efforts to reform or enhance public policies regarding wildlife management and biodiversity conservation. However, mainstreaming adaptation into decision making is a continual process where vulnerability should be periodically reassessed as new knowledge, learning, and insights become known.