Global deforestation peaked in the 1980s. Can we bring it to an end?

Since the end of the last ice age — 10,000 years ago — the world has lost one-third of its forests.¹ Two billion hectares of forest — an area twice the size of the United States — has been cleared to grow crops, raise livestock, and for use as fuelwood.

Previously, we looked at this change in global forests over the long run. What this showed was that although humans have been deforesting the planet for millennia, the rate of forest loss accelerated rapidly in the last few centuries. Half of the global forest loss occurred between 8,000 BCE and 1900; the other half was lost in the last century alone.

To understand this more recent loss of forest, let’s zoom in on the last 300 years. The world lost 1.5 billion hectares of forest over that period. That’s an area 1.5 times the size of the United States.

In the chart, we see the decadal losses and gains in global forest cover. On the horizontal axis, we have time, spanning from 1700 to 2020; on the vertical axis, we have the decadal change in forest cover. The taller the bar, the larger the change in forest area. This is measured in hectares; one hectare is equivalent to 10,000 m².

Forest loss measures the net change in forest cover: the loss in forests due to deforestation plus any increase in forest through afforestation or natural expansion.²

Unfortunately, there is no single source that provides consistent and transparent data on deforestation rates over this period of time. Methodologies change over time, and estimates — especially in earlier periods — are highly uncertain. This means I’ve had to use two separate datasets to show this change over time. As we’ll see, they produce different estimates of deforestation for an overlapping decade — the 1980s — which suggests that these are not directly comparable. I do not recommend combining them into a single series, but the overall trends are still applicable and tell us an important story about deforestation over the last three centuries.

The first series of data comes from Williams (2006), who estimates deforestation rates from 1700 to 1995.³ Due to poor data resolution, these are often given as average rates over longer periods — for example, annual average rates are given over the period from 1700 to 1849 and 1920 to 1949. That’s why these rates look strangely consistent over a long period of time.

The second series comes from the UN Food and Agriculture Organization (FAO). It produces a new assessment of global forests every five years.⁴

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The rate and location of forest loss changed a lot. From 1700 to 1850, 19 million hectares were being cleared every decade. That’s around half the size of Germany.

Most temperate forests across Europe and North America were being lost at this time. Population growth meant that today’s rich countries needed more and more resources such as land for agriculture, wood for energy, and construction.⁵

Moving into the 20th century, there was a stepwise change in demand for agricultural land and energy from wood. Deforestation rates accelerated. This increase was mostly driven by tropical deforestation in countries across Asia and Latin America.

Global forest loss appears to have reached its peak in the 1980s. The two sources do not agree on the magnitude of this loss: Williams (2006) estimates a loss of 150 million hectares — an area half the size of India — during that decade.

Interestingly, the UN FAO 1990 report also estimated that deforestation in tropical ‘developing’ countries was 154 million hectares. However, it was estimated that the regrowth of forests offset some of these losses, leading to a net loss of 102 million hectares.⁶

The latest UN Forest Resources Assessment estimates that the net loss in forests has declined in the last three decades, from 78 million hectares in the 1990s to 47 million hectares in the 2010s.

This data maps an expected pathway based on what we know from how human-forest interactions evolve.

As we explore in more detail later on, countries tend to follow a predictable development in forest cover, a U-shaped curve.⁷ They lose forests as populations grow and demand for agricultural land and fuel increases, but eventually, they reach the so-called ‘forest transition point’ where they begin to regrow more forests than they lose. This can include both natural restoration, and forest plantations, which can have very different impacts from a biodiversity perspective.

That is what has happened in temperate regions: they have gone through a period of high deforestation rates before slowing and reversing this trend.

However, many countries — particularly in the tropics and sub-tropics — are still moving through this transition. Deforestation rates are still very high.

Deforestation rates are still high across the tropics

Large areas of forest are still being lost in the tropics today. This is particularly tragic because these are regions with the highest levels of biodiversity.

Let’s look at estimates of deforestation from the latest UN Forest report. This shows us raw deforestation rates without any adjustment for the regrowth or plantation of forests, which is arguably not as good for ecosystems or carbon storage.

This is shown in the chart below.

We can see that the UN does estimate that deforestation rates have fallen since the 1990s. However, there was very little progress from the 1990s to the 2000s and an estimated 26% drop in rates in the 2010s. In 2022, the FAO published a separate assessment based on remote sensing methods; it did not report data for the 1990s, but it also estimated a 29% reduction in deforestation rates from the early 2000s to the 2010s.

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This is progress, but it needs to happen much faster. The world is still losing large amounts of primary forests every year. To put these numbers in context, during the 1990s and first decade of the 2000s, an area almost the size of India was deforested.⁸ Even with the ‘improved’ rates in the 2010s, this still amounted to an area around twice the size of Spain.⁹

The regrowth of forests is a positive development. In the chart below, we see how this affects the net change in global forests. Forest recovery and plantation ‘offsets’ a lot of deforestation such that the net losses are around half the rates of deforestation alone.

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But we should be cautious here: it’s often not the case that the ‘positives’ of regrowing on planting one hectare of forest offset the ‘losses’ of one hectare of deforestation. Cutting down one hectare of rich tropical rainforest cannot be completely offset by the creation of on hectare of plantation forest in a temperate country.

This is especially true when we consider how that forest is grown or used. In some temperate countries — such as in the United Kingdom — a large part of forested area is in the form of single and non-native species plantations, which doesn’t have the same biodiversity benefits as natural regrowth.

Forest expansion is generally positive but does not negate the need to end deforestation.

The history of deforestation is a tragic one, in which we have lost not only wild and beautiful landscapes but also the wildlife within them. But, the fact that forest transitions are possible should give us confidence that a positive future is possible. Many countries have not only ended deforestation but have actually achieved substantial reforestation. It will be possible for our generation to achieve the same on a global scale and bring the 10,000-year history of forest loss to an end.

If we want to end deforestation, we need to understand where and why it’s happening, where countries are within their transition, and what can be done to accelerate their progress through it. We need to pass the transition point as soon as possible while minimizing the amount of forest we lose along the way.

In this article, I look at what drives deforestation, which helps us understand what we need to do to solve it.

Forest definitions and comparisons to other datasets

There is no universal definition of what a ‘forest’ is. That means there are a range of estimates of forest area and how this has changed over time.

In this article, in the recent period, I have used data from the UN’s Global Forest Resources Assessment (2020). The UN carries out these global forest stocktakes every five years. These forest figures are widely used in research, policy, and international targets, such as the Sustainable Development Goals.

The UN FAO has a very specific definition of a forest. It’s “land spanning more than 0.5 hectares with trees higher than 0.5 meters and a canopy cover of more than 10%, or trees able to reach these thresholds in situ.”

In other words, it has criteria for the area that must be covered (0.5 hectares), the minimum height of trees (0.5 meters), and a density of at least 10%.

Compare this to the UN Framework Convention on Climate Change (UNFCCC), which uses forest estimates to calculate land use carbon emissions, and its REDD+ Programme, where low-to-middle-income countries can receive finance for verified projects that prevent or reduce deforestation. It defines a forest as having a density of more than 10%, a minimum tree height of 2-5 meters, and a smaller area of at least 0.05 hectares.

It’s not just forest definitions that vary between sources. What is measured (and not measured) differs, too. Global Forest Watch is an interactive online dashboard that tracks ‘tree loss’ and ‘forest loss’ across the world. It measures this in real time and can provide better estimates of year-to-year variations in rates of tree loss.

However, the UN FAO and Global Forest Watch do not measure the same thing.

The UN FAO measures deforestation based on how land is used. It measures the permanent conversion of forested land to another use, such as pasture, croplands, or urbanization. Temporary changes in forest cover, such as losses through wildfire or small-scale shifting agriculture, are not included in deforestation figures because it is assumed that they will regrow. If the use of land has not changed, it is not considered deforestation.

Global Forest Watch (GFW) measures temporary changes in forests. It can detect changes in land cover but does not differentiate the underlying land use. All deforestation would be considered tree loss, but a lot of tree loss would not be considered as deforestation.

As GFW defines ‘forest loss’, “Loss” indicates the removal or mortality of tree cover and can be due to a variety of factors, including mechanical harvesting, fire, disease, or storm damage. As such, “loss” does not equate to deforestation.”

Therefore, we cannot directly compare these sources. This article from Global Forest Watch gives a good overview of the differences between the UN FAO's and GFW's methods.

Since GFW uses satellite imagery, its methods continually improve. This makes its ability to detect changes in forest cover even stronger. But it also means that comparisons over time are more difficult. It currently warns against comparing pre-2015 and post-2015 data since there was a significant methodological change at that time. Note that this is also a problem in UN FAO reports, as I’ll soon explain.

What data from GFW makes clear is that forest loss across the tropics is still very high, and in the last few years, little progress has been made. Since UN FAO reports are only published in 5-year intervals, they miss these shorter-term fluctuations in forest loss. The GFW’s shorter-interval stocktakes of how countries are doing will become increasingly valuable.

One final point to note is that UN FAO estimates have also changed over time, with improved methods and better access to data.

I looked at how net forest losses in the 1990s were reported across five UN reports: 2000, 2005, 2010, 2015, and 2020.

Estimated losses changed in each successive report:

• 2000 report: Net losses of 92 million hectares
• 2005 report: 89 million hectares
• 2010 report: 83 million hectares
• 2015 report: 72 million hectares
• 2020 report: 78 million hectares

This should not affect the overall trends reported in the latest report: the UN FAO should — as far as is possible — apply the same methodology to its 1990s, 2000s, and 2010s estimates. However, it does mean we should be cautious about comparing absolute magnitudes across different reports.

This is one challenge in presenting 1980 figures in the main visualization in this article. Later reports have not updated 1980 figures, so we have to rely on estimates from earlier reports. We don’t know whether 1980s losses would also be lower with the UN FAO’s most recent adjustments. If so, this would mean the reductions in net forest loss from the 1980s to 1990s were lower than is shown from available data.

Hannah Ritchie (2021) - “Global deforestation peaked in the 1980s. Can we bring it to an end?” Published online at OurWorldinData.org. Retrieved from: 'https://ourworldindata.org/global-deforestation-peak' [Online Resource]

@article{owid-global-deforestation-peak,
    author = {Hannah Ritchie},
    title = {Global deforestation peaked in the 1980s. Can we bring it to an end?},
    journal = {Our World in Data},
    year = {2021},
    note = {https://ourworldindata.org/global-deforestation-peak}
}

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