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Is carbon protection the same as biodiversity protection? Commentary by Amy Hinsley of Fauna and Flora International (FFI) September 05, 2010 Why biodiversity matters for carbon storage
There has been debate about the potential impacts of REDD schemes on biodiversity, given its potential to protect natural forests (1). However, where REDD projects are not well designed, they could fail to effectively protect the biodiversity within the forest itself; protecting these areas for their carbon value may not necessarily conserve their biodiversity value. Furthermore, relatively little is known about how such reductions in biodiversity may in turn affect the ability of a forest to store carbon (2).
Although habitat destruction remains a key global threat to biodiversity, simply protecting forest cover does not necessarily prevent a loss of the species within. If not managed effectively then threats such as uncontrolled hunting, selective logging or collection of non-timber forest products may alter both biodiversity levels and species composition. This will have direct impacts, but may also have indirect impacts on the resilience of the ecosystem, and thus its ability to store carbon in the long term (3). For example, one study suggested “Even forests whose trees received full protection from a program such as REDD could, over decades, lose carbon stocks through the ripple effects of bushmeat hunting on species interactions” (4). Direct effects of biodiversity loss on carbon storage REDD initiatives are designed to control threats related to trees, such as selective logging, fires or destructive collection of tree products. However, they may not necessarily protect against the loss or destruction of non timber plants or collection of animals. One of the most interesting examples of the potential impact of biodiversity loss on carbon storage is the case of hunting – be it for bushmeat or for commercial use – activities that are widespread across many forested areas.
Bushmeat hunting of species which act as seed dispersers may result in a shift in tree species composition, and could ultimately alter carbon storage potential - although this process is still the subject of debate. Field studies in Thailand, Cameroon and Panama have found that 70%-90% of tree species rely on animal seed dispersal and that bushmeat hunting has a direct impact on tree species composition (4,6,7). In Cameroon and Thailand, the removal of large bodied seed dispersers was linked to the loss of larger seeded trees, which are often those that store the most carbon. However, others have questioned the impact of bushmeat hunting on carbon storage, given an associated reduction in seed predation8. Changes in species composition – implications for carbon? There is evidence that the loss of vertebrate seed dispersers can shift plant species composition towards those with wind dispersed seeds, such as lianas. This can result in a reduction in the net carbon stored in the forest. For example, lianas grow quickly and are able to out-compete slower growing trees for both light, water and soil nutrients (9,10). This inhibits tree growth and regeneration, and increases tree mortality. An increase in lianas within a forest has been shown to negatively affect both the rate and volume of carbon storage. This occurs for two reasons: firstly while lianas out-compete trees, their thin stems and low wood density mean that they store relatively little carbon compared to the trees which they replace (10). Secondly, lianas will infest certain species preferentially, causing a shift in species composition to faster growing tree species, which often have lower wood density and store much less carbon (11). One model predicts a 34% decrease in carbon storage of a forest following liana infestation (2). Biodiversity loss and ecosystem resilience Unpredictable disturbances such as fires, natural disasters and invasive species introductions - and the ongoing changes to temperature or precipitation caused by climate change - all require ecosystems to adapt. Resilience of an ecosystem (its ability to recover from such impacts) is a key concern – as a degraded forest ecosystem quickly ceases to be a carbon sink and becomes a carbon source. High levels of biodiversity can provide ‘biological insurance’ against losses from disturbances, making the ecosystem more resilient and likely to recover, and allowing it to continue storing carbon in the long term (2). A 2009 report by the CBD supported this, stating that “within a given biome, diverse forests are more biologically productive and provide larger and more reliable carbon stocks, especially in old-age stable forest systems...Hence, protecting and restoring biodiversity serves to maintain resilience in forests, in time and space, and their ongoing capacity to reliably sequester and store carbon” (12). For example, a large fire may destroy several dominant trees and plants, but quickly colonizing plant species will take their place, producing the appropriate environment to enable the subsequent recovery of larger, dominant species (2). This recovery is only possible if a diversity of species co-exist in the first place.
Resilience to the changing climate is also becoming a more important issue and biodiversity is likely to strengthen an ecosystem’s ability to survive without significant loss of above-ground carbon storage. One study concluded that biodiverse ecosystems in Panama are likely to show greater resilience to a drying climate as the presence of several drought tolerant species provides ‘biological insurance’ to counter the loss of other species2. Additional indirect benefits of protecting biodiversity Building biodiversity protection within REDD schemes adds extra value, beyond enhanced carbon protection (15). Maintaining biodiversity maintains other non- carbon functions of forests – for both local communities and wider ecosystem service benefits - including opportunities for sustainable harvests, but also maintenance of services such as water quality and pollination and erosion prevention.
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(07/22/2010) Scientists convening in Bali expressed a range of concerns over a proposed mechanism for mitigating climate change through forest conservation, but some remained hopeful the idea could deliver long-term protection to forests, ease the transition to a low-carbon economy, and generate benefits to forest-dependent people.
(12/08/2009) Destruction of old-growth or primary forests looms large in discussions in Copenhagen over a scheme to compensate tropical countries for reducing emissions from deforestation and degradation (REDD). Some environmental groups are pressing for conservation of old-growth forests — the most carbon-dense, and biologically-rich state of forests — to be the centerpiece of REDD, while industry and other actors are pushing for "sustainable forest management" or logging using reduced-impact techniques to be the primary focus of REDD.
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