Will tropical forests survive a changing climate?

Most people are familiar with tree-planting as a way to offset carbon emissions. However, while the focus has been on reforestation and preventing deforestation, there has been little emphasis on how the world's tropical forests, managed for production purposes, will actually be able to adapt to the changing climate. According to a new study, there is an urgent need to put measures in place to ensure that the world's tropical forests will survive.

Tropical forests are not just carbon sinks nor large carbon storehouses; they also make a major contribution to many national and rural economies. Temperatures and rainfall are predicted to become unstable, and an increase in the intensity of extreme weather events in such tropical areas threatens forests'survival.

The speed and human-driven nature of change might be beyond forests' natural capacity to adapt. However, since many countries perceive more immediate threats to their forests, such as those from pasture expansion and illegal logging, the threat posed by climate change has been overlooked. A team of researchers has now outlined measures that could help tropical forests to maintain their capacity to deliver goods and services under a changing climate and, in turn, the livelihoods of those who depend upon them.

According to the study, practical guidance and funding to implement the necessary measures are needed now. Some of these measures could be easily incorporated into current forestry management. For example, when selection pressure is strongest (e.g. at the seedling stage) the number of juvenile timber trees could be increased. This could be achieved relatively simply through site preparation to establish seedlings (for example controlled burning in Central American closed cone pine forests), thinning to promote crown development (possibly as part of controlled logging) and eventual fruiting of seed trees and harmonising the timing of tree harvesting to follow seed dispersal.

Efforts could also be made to increase the diversity of planted tree species, in order to establish species that will survive the changing environment. Translocation of tree seedlings and seeds and the maintenance of tree corridors would also allow greater natural seed dispersal, and enable natural, evolutionary adaptation to varying climatic conditions.

However, natural selection may need help in some cases. Enrichment planting of species at risk already takes place in the Brazilian rainforest, where it is mandatory to plant mahogany seedlings. It will become necessary to expand this to other threatened species as climate pressure increases. The choice of species that are planted should also come under regular review. This is particularly important for smallholders, who may be dependent on one species in a single plantation, and will need to be supported.

Practical guidelines need to be devised to indicate which forest management strategies can increase forests' capacity to adapt in order to ensure long-term management objectives.

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