This paper reviews the concepts of ecosystem resilience, resistance, and stability in forests and their relationship to biodiversity, with particular reference to climate change.
The report is a direct response to a request by the ninth meeting of the Conference of the Parties to the CBD, in decision IX/5, to explore the links between biodiversity, forest ecosystem resilience, and climate change. Forests are emphasized because they are major reservoirs of terrestrial biodiversity and contain about 50% of the global terrestrial biomass carbon stocks. Emissions from deforestation and degradation remain a significant source of annual greenhouse gas emissions into the atmosphere, and therefore the conservation, appropriate management and restoration of forests will make a significant contribution to climate change mitigation. Further, forests have a certain natural capacity to adapt to climate change because of their biodiversity. Some animals have important roles in ecosystem processes and organization, such as pollination, seed dispersal, and herbivory, and the loss of these species has clear negative consequences for ecosystem resilience. Here, however, wi limit our discussion to botanical aspects of forests, with the excepcion of some discussion of insect pests and diseases as these influence forest resilience and stability.
Forests have many unique properties, related to their high rates of primary productivity and biodiversity, which distinguish them ecologically from other ecosystems. Such properties include biological structures that develop in vertical and horizontal layers of live and dead plant, complex processes at multiple vertical levels from within soil layers up to the canopy, the capacity for self-renewal in the face of constant small and large disturbances, co-evolved plan-animal and plant-plant interactions, and the influence forest landscapes can have on micro canopy tropical forests. Forests are comprised of multiple ecosystems that are associated with variable edaphic and microclimate conditions across broad landscapes.
Humans are having long-term cumulative impacts on Earth's ecosystems through a range of consumptive, exploitive, and indirect mechanisms, even to the extent of influencing the global climate. The major impacts of humans on forest ecosystems include loss of forest area, habitat fragmentation, soil degradation, depletion of biomass and associated carbon stocks, transformation of stand age and species composition, species loss, species introductions, and the ensuing cascading effects, such as increasing risk of fire. As a result, there has long been global concern about the long-term capacity of forests to maintain their biodiversity and associated rates of supply of goods and services. This concern has been amplified following observed impacts occurring to global forests as a result of climate change.