Optimising the recovery of degraded tropical rainforest logging

Tropical rainforests are an extraordinary and important habitat: they are some of the most biodiverse places on Earth and are a vital part of the global carbon cycle, locking away carbon dioxide in trees. The valuable hardwoods in tropical rainforests are also a key source of income for many countries, but these trees are slow growing and increasingly rare. As a result, many countries now have huge areas of degraded, logged forest and the net income from timber production is declining as valuable trees become harder to find and more expensive to extract. In many countries, these degraded forests are simply cleared and used for other activities, such as palm oil production, grazing or woodlots for fast-growing tree species.

There is a more positive alternative future that could be secured for these degraded forests: allowing them to regenerate to restore stocks of high value hardwoods and promote carbon capture. That is a long-term investment - hardwoods take many decades to grow to a size where they can be logged - so to give the necessary breathing space in the short term, fast-growing species planted within degraded forest could provide an ongoing harvest of less valuable timber while the forest recovers.

This approach - called mosaic planting - might provide a win-win situation for local economies and global conservation: forests recover while generating income. However, it could also be lose-lose: harvesting and planting damage the forest too badly and the commercial timber grows too slowly to provide a good return. So, where does the answer lie? This project will address this urgent question.

Getting direct answers is a challenge. Rainforests grow too slowly to conduct experiments and see what happens, and we can't wait a generation to work out how best to manage forests today. Our solution is to use virtual experiments instead. Simulating rainforest growth is a lot easier, many times faster and very much less risky than experimenting with the real world.

In this project, we will develop an individual-based simulation of tropical rainforest tree communities, and apply it to the real-world problem of optimising the restoration of degraded logging estates. The model will simulate the birth, growth and mortality of tree functional groups, based on the key photosynthesis and respiration processes that operate at the scale of individual trees and tracking the cycling of water and carbon. It will build on a number of existing simulations, but provide greater flexibility to examine management scenarios, including variation in forest starting conditions and specific management options such as planting density, planting composition, liana cutting and logging frequency, all within the context of wider global climate change. We will calibrate and validate the model using extensive empirical field data available from the SAFE Project study site in Sabah, Malaysia.