Tropical forest degradation in the context of climate change: increasing role and research challenges. [K-2215-01]

While developed countries in temperate regions faced their forest transition about 100 years ago or more, “tropical forest rich” nations still largely depend on forest resources or land clearing for their development. Hence, tropical forests are retreating at an alarming rate from advancing cash crops, such as oil palm, soybean, or cattle ranching. Beside tropical deforestation, tropical forest degradation resulting mostly from human-induced causes (e.g. predatory or illegal logging, non-timber forest product extraction, fuel wood extraction) significantly contributes to greenhouse gas emissions and loss of biodiversity. If deforestation is an obvious ecosystem change, forest degradation is more difficult to discern and quantify. Degraded forests have become a major component of today's tropical landscapes, representing up to 50 % of all tropical forests. For example, almost half of standing primary tropical forests, up to 400 million ha, are designated by national forest services for timber production. The portion of tropical forests managed for timber extraction, hereafter referred to as “managed forests”, will therefore play key roles in the trade-off between provision of goods and maintenance of carbon stocks, biodiversity, and other services. However, so far, most of our understanding of tropical forest arise from studies carried out in old-growth undisturbed forests, or secondary forests (i.e. regrowth forests) while the ecology of degraded forests at the regional and continental scale remains poorly studied and their role to mitigate climate change still very poorly known. However, understanding the functions played by degraded forests in providing goods and environmental services in the context of climate change is crucial. We will first discuss the complex concept of forest degradation in the tropics and then define degraded forests. We will show their importance in providing timber while maintaining high levels of biodiversity and carbon stocks. We will further demonstrate that implementation of sustainable forest management can promote long term provision of ecosystem services. Finally, the potential of tropical degraded forests in mitigating climate change will be discussed along with future research challenges on this issue. (Texte intégral)