What is deforestation and forest degradation, and what do these have to do with climate change?
Deforestation is the mass destruction of trees. Forests account for about 30 percent of the world’s land, but human activities are contributing to massive forest loss. Between 1990 and 2016, about 1.3 million square kilometers of forest cover was lost — an area larger than the size of South Africa. The majority of the world’s forest loss has occurred in the tropics.
As trees grow and forests expand, so does the amount of carbon dioxide stored in them. The destruction of forests leads to the release of carbon dioxide stored in trees and soils into the atmosphere. Currently, the world’s forests absorb about a third of man-made carbon emissions.
Net emissions from deforestation are the balance of carbon dioxide released and absorbed by forest destruction and expansion. According to the Intergovernmental Panel on Climate Change (IPCC) report on land and climate change, from 2007 to 2016, net carbon dioxide emissions from land use and land-use change were about 5.2 ± 2.6 GtCO2 yr-1 — about a quarter of global carbon emissions released from human activities in 2018. The majority of these emissions were due to deforestation, partially offset by afforestation or reforestation, and emissions and removals by other land use activities.
Forest degradation occurs when some trees are removed but the forest remains. According to published research, carbon emissions from tropical forest degradation account for about one-third of emissions from deforestation. Interestingly, for a third of the countries included in the analysis, emissions from forest degradation were even higher than those from deforestation. Research also suggests that the figures for forest degradation may be underestimated, and if taken into account, could double the emissions from deforestation.
Source: A deforested area near Novo Progresso in Brazil’s northern state of Para (Insider, 2020)
Continued deforestation will make it difficult to meet climate targets, and in order to avoid dangerous warming, deforestation needs to be reduced. A quarter of emissions reductions pledged by countries through the Paris climate change agreement comes from avoiding deforestation and better management of forests.
What are the causes of deforestation and forest degradation?
Brazil and Indonesia are highly vulnerable to forest degradation and deforestation. Cattle ranching and soy production are the main drivers of deforestation in Brazil. Cattle ranching is the top economic activity of the Amazonia region, and ranches cover about 80 percent of deforested areas. Between 2015 and 2017, an estimated 51 percent of deforestation came from cattle raised in the Amazon. In the Cerrado region of Brazil, soy fields have expanded to more than 9 million hectares between 2000-2017 (35,000 square miles of land), with more than 50 percent of its natural vegetation being lost. This deforestation is also threatening its water supplies and increasing the risk of fires in the Amazon, its neighboring region.
In Indonesia, the demand for land for palm oil plantations is one of the main factors behind deforestation. Analysis of forest fires in Indonesia by the World Resources Institute also suggests that pulpwood production and logging are factors behind deforestation. Much of this deforestation is occurring in mature natural forests. Some of these forests are replaced with commercial plantations, reducing biodiversity and native species.
Source: Deforestation in Jambi Province, Sumatra, Indonesia. (Rainforest Action Network, Indonesia)
Impact of climate change on tropical deforestation in the Amazon
Climate change and increasing greenhouse gas (GHG) emissions are also making forests drier and are increasing the risks of wildfires. Previous research has shown that drought has led to an increase in fires in the Amazon rainforest. In the Brazilian Amazon, more than half the emissions for 2005, 2007, 2010, and 2015 came from fires.
Source: Trees after forest fires in Mato Grosso, Brazil in 2008. (Rodrigo Baleia for The Guardian, 2017)
The Amazon rainforest is also a major carbon sink, which two decades ago was drawing two billion tonnes of carbon dioxide out of the atmosphere each year. However, as the amount of carbon dioxide in the atmosphere rises, trees are both growing and dying faster. The Amazon’s ability to soak up carbon has fallen by half since the 1990s, according to one 30-year study. As the amount of carbon in the atmosphere increases, tropical rainforests’ ability to act as a carbon store may be levelling off.
How does deforestation contribute to climate change?
Deforestation is a key driver of climate change and land degradation. Globally more than 60 percent of forests are under some form of use or management by humans. Deforestation and degradation of forests accounted for 69 percent of losses of forest biomass across the tropics, with some models showing that tropical forests are a modest source of carbon emissions. One estimate suggests the degradation of tropical forests releases around 2.1 billion tonnes of carbon dioxide annually, of which 53% is from timber harvest, 30% from wood fuel harvest and 17% from forest fires.
Estimates suggest that if the current rate of deforestation is maintained over the next few years, the Amazon could reach a “tipping point” as soon as 2021. Through evaporation and transpiration, tropical rainforests can produce as much as 75 percent of their own rain. If the Amazon reaches this tipping point, it will lose the ability to generate sufficient rain to sustain itself.
Planting more trees could help limit climate change
Planting more trees and restoring forests (afforestation and reforestation, or AR) would absorb more carbon dioxide, and could be part of global measures aimed at reducing emissions to limit climate change. Reforestation is the process of converting previously forested land back into the forest, whereas afforestation is the process of planting forests on lands where they did not previously grow. According to IPCC, AR has the potential to remove 0.5–10.1 GtCO2-eq per year. This could help the world avoid crossing dangerous climate change thresholds.