Forests play an absolutely vital role in the fight against climate change. Without trees our planet would become uninhabitable. They are a source of food, medicines and biofuel for more than 1 billion people. They protect soils and water and host more than threequarters of the world’s terrestrial biodiversity. Forests provide many products and services that contribute to socio-economic development and create work and income for tens of millions of people.

But above all, they are a vast sink for carbon dioxide.

In her excellent article on deforestation, Hannah Ritchie (Deputy Editor and Lead Researcher at Our World in Data) points out that:

Deforestation rates increased dramatically from 1900 onward. A rapidly growing population needed more food. Agriculture demanded more space to grow crops and graze livestock. Even in 2025, it still does.

Deforestation is currently responsible for 11% of carbon emissions. When trees are felled, CO2 is released into the atmosphere and less CO2 is absorbed from the atmosphere. It’s lose/lose. According to the Food and Agriculture Organisation’s (FAO) Rome report: Global Forest Resources Assessment 2020 (the go-to resource for reliable data on deforestation), the rate of forest loss in the world is decreasing but deforestation still goes on.

Much confusion surrounds exactly what is meant by deforestation. It's not simply the cutting down of trees. There's a clear distinction between forest degradation and deforestation.

• Forest degradation is the logging of managed plantations, wildfires or shifting agriculture. The expectation is that the land will eventually return to forest.

• Deforestation is the permanent conversion of forest to another land use, usually agriculture and to a smaller extent, urbanisation.

Climate scientists are most worried about deforestation since there is little hope of ever seeing this land return to mature forest. It is lost forever. However, around the world, aborists are planting new forests in a desperate attempt to offset deforestation. While it is mitigating the impact of deforestation, this afforestation is not competing with the ongoing rate of forest loss in countries like Brazil and Indonesia. (See Fig. 2 below.)

“Half of the global forest loss occurred between 8,000 BCE and 1900; the other half was lost in the last century alone.”

Figure 2

It’s apparent from the above chart that afforestation or forest regrowth is vital to lessen the impact of deforestation. The 110 million hectares of forest destroyed between 2010 and 2019 becomes a net loss of 47 million hectares owing to 63 million hectares of afforestation.

In order to plug the 11% of global carbon emissions that deforestation is contributing each year, firstly and most importantly, deforestation must stop and secondly, afforestation projects must be a mandatory part of every country’s climate commitment.

Where is today’s deforestation taking place?

Figure 3

95% of deforestation is the felling or deliberate burning of tropical forest of which half is in Brazil and Indonesia. Three screenshots from Google Earth are all it takes to highlight the problem.

Fig. 4 shows deforestation in Rondônia in western Brazil. The classic herring bone pattern shows major roads driven through the forest (the backbones) after which minor roads (the ribs) extend out at regular intervals as farmers claim and clear land for agriculture.

Credit: NASA

Figure 4

Fig 5 below was taken in 2024 and shows the characteristic grid layout of Indonesia’s palm oil plantations.

Credit: Airbus

Figure 5

Fig 6 is a close-up view of part of Fig 5 and clearly shows the endless lines of oil palm trees, a classic monoculture where once stood dense rain forest.

Figure 6

Hidden behind the alarming deforestation statistics in Brazil and Indonesia, another catastrophe is developing, a tipping point that is showing alarming signs of starting its tip.

In July 2021, climate scientists Luciana V. Gatti et al. published a paper in Nature which reported that the south-eastern Amazon forest was no longer a CO2 sink, but rather, because of forest loss and associated fires, it was a source of CO2.

The Amazon rainforest has always been regarded as one of the planet’s major carbon sinks, removing vast quantities of CO2 from the atmosphere. Homo sapiens has relied on the forest to mop up sufficient quantities of the gas to mitigate the worst effects of climate change. But that is in the process of changing.

Conversion of rainforest to agriculture has caused a 17 percent decrease in forest extent in the Amazon. Replacing dense, humid forest canopies with drier pastures and cropland has increased local temperatures and decreased evaporation of water from the rainforest. In a forest, water evaporates from leaves in huge volumes. 25-35% of the total rainfall in the Amazon basin results from this evaporation. As a result, the Amazon gets between six and ten feet of rainfall each year. But deforestation and forest degradation has reduced rainfall in parts of southeast Amazonia. In 2020, rainfall decreased by 12% and the average temperature increased by 0.6%. Without sufficient rain, the remaining forest cannot survive. The less forest, the less rain, the less forest, the less rain…. positive feedback, irreversible change. And all the while, the less forest, the less CO2 sink, the higher atmospheric CO2 concentrations, the higher the global temperature.

The maps below show annual precipitation in South America in 2013 and 2023. They are averages taken across the whole of each country and do not show local variation.

Figure 7

Surely somewhere amid these dire statistics, there is some good news. And there is.

The chart below plots deforestation in the Brazilian Amazon in km2 for each year between 1988 and 2024. Beneath each year bar is the president in power in Brazil at that time.

Hannah Ritchie: OurWorldinData - Source INPE, (PRODES)

Figure 9

Lula da Silva was elected president in 2003. He served two terms of 4 years each. During his presidency, deforestation rates in the Brazilian rainforest fell by 75%.

Then in 2018, Jair Bolsonaro was elected. In Bolsonaro’s four years in power, vast tracts of the Amazon fell to make way for mining, cattle ranches, and soybean farming. During his tenure from 2019 to 2022, Bolsonaro’s administration weakened regulation and enforcement around deforestation, shrinking the budgets of agencies monitoring environmental crimes and pushing for laws allowing forest-destroying mining on indigenous land. Now Lula da Silva’s return has given new hope to those fighting to save the forest.

Title photo: By Planet Labs, Inc. - https://www.planet.com/gallery/fishbone-deforestation-20160805/ (direct link), CC BY-SA 4.0 Deforestation in Rondônia, Brazil