How Deforestation is Disrupting our Biodiversity

Original Content: AXA Research Fund

We have seen very significant deforestation in recent years to make way for crops such as oil palm or acacia. What is the effect on biodiversity?

Dr. Vincent Gauci: The character of the landscape changes dramatically, from many hundreds of different plant species per hectare to maybe one or two. With oil palm, we have also seen proliferation of rats – so there is a whole range of other species coming in. We know there has been a 50% loss in orangutans over the last twenty years due to deforestation and we are down to the last 300 or so Sumatran tigers in the wild. It has a very disruptive effect.

After deforestation, do these landscapes become more susceptible to climate change?

Dr. Vincent Gauci : Yes – we are moving towards a system that does not have the same level of resilience and is not able to adjust to climate shocks. In south-east Asia, for example, we are talking about wet, carbon-rich ecosystems. They do not ignite, they do not burn. Once the trees are removed and the peat is drained for agriculture to make room for plantations, the peat15 becomes very dry and it becomes susceptible to fire. 

And this releases carbon and adds to climate change

Dr. Vincent Gauci : Yes – peatlands are enormous stores of carbon. Fires occur every summer in south-east Asia. In 2015, during the last big El Niño event, there were huge fires across tracts of land in Sumatra and elsewhere. There is also carbon release just through drainage. When trees are cut down, channels are cut into the peat to drain the land, resulting in an upper meter or so of peat that is then exposed to oxygen, while it has not been exposed for thousands of years. Carbon and oxygen produce aerobic decomposition – when organic materials decompose in the presence of oxygen, and carbon rapidly disappears into the atmosphere as CO2. 

How does deforestation affect the land?

Dr. Vincent Gauci : It can create artificial boundaries. The hydrology of peatland is such that, if a portion is drained, it will have knock-on effects many hundreds of meters or even kilometers away. This is not unknown to local land managers who will do their best to limit hydrology loss. The management of water in these landscapes is quite a challenge as water can be lost very quickly. Deforestation might also cause encroachment – for example, tigers moving out and seeking food elsewhere, leading  to the additional challenge of human-species interaction.

Around the world, the scale of deforestation has been enormous. Do you see attitudes changing?

Dr. Vincent Gauci : The Amazon is being depleted at the rate of a football pitch of tropical forest every minute. This is very politically sensitive. In Brazil, some land users now feel they can deforest again because of the recent change of government. Elsewhere, in south-east Asia for example, there are moratoriums in place – ironically, some of the big landholders end up almost ‘policing’ the fragments of natural forest that remain. It is a very complex situation and tensions arise. For example If you build a road, for economic development so that a community can get greater access to markets, more people will come into the forest that the road cuts through; they may lay claim to the land through legal or illegal means with often little policing or resistance, and clear the forest for crops or other products. The challenge is really about people, their movement and livelihoods and balancing the needs for economic development with protection of the forest. And this crosses borders – commodities grown in tropical forests are part of international markets – with palm oil and paper, and so on. 

What are the possible solutions? How do we protect these forests?

 Dr. Vincent Gauci: There are efforts to reforest – that can bea solution. In Indonesia, after the 2015 fires,landholders were told to raise the water table in peatland to within forty centimeters of the surface. That provides an opportunity to go back to native tree species that do not grow as quickly, but that grow well in a high-water table environment. It is not easy to raise the water table, but it can be done by introducing dams and sluices and regulating flows through drainage canals. There are a lot of issues relating to this, but landholders are starting to realize that their long-term economic sustainability depends on not losing their peat.