Not all forest loss is equal: what is the difference between deforestation and forest degradation?

15 billion trees are cut down every year.¹ The Global Forest Watch project – using satellite imagery – estimates that global tree loss in 2019 was 24 million hectares. That’s an area the size of the United Kingdom.

These are big numbers, and important ones to track: forest loss creates a number of negative impacts, ranging from carbon emissions to species extinctions and biodiversity loss. But distilling changes to this single metric – tree or forest loss – comes with its own issues.

The problem is that it treats all forest loss as equal. It assumes the impact of clearing primary rainforest in the Amazon to produce soybeans is the same as logging planted forests in the UK. The latter will experience short-term environmental impacts, but will ultimately regrow. When we cut down primary rainforest we are transforming this ecosystem forever.

When we treat these impacts equally we make it difficult to prioritize our efforts in the fight against deforestation. Decisionmakers could give as much of our attention to European logging as to destruction of the Amazon. As we will see later, this would be a distraction from our primary concern: ending tropical deforestation. The other issue that arises is that ‘tree loss’ or ‘forest loss’ data collected by satellite imagery often doesn’t match the official statistics reported by governments in their land use inventories. This is because the latter only captures deforestation – the replacement of forest with another land use (such as cropland). It doesn’t capture trees that are cut down in planted forests; the land is still forested, it’s now just regrowing forest.

In the article we will look at the reasons we lose forest; how these can be differentiated in a useful way; and what this means for understanding our priorities in tackling forest loss.

Understanding and seeing the drivers of forest loss

‘Forest loss’ or ‘tree loss’ captures two fundamental impacts on forest cover: deforestation and forest degradation.

Deforestation is the complete removal of trees for the conversion of forest to another land use such as agriculture, mining, or towns and cities. It results in a permanent conversion of forest into an alternative land use. The trees are not expected to regrow. Forest degradation measures a thinning of the canopy – a reduction in the density of trees in the area – but without a change in land use. The changes to the forest are often temporary and it’s expected that they will regrow.

From this understanding we can define five reasons why we lose forests:

• Commodity-driven deforestation is the long-term, permanent conversion of forests to other land uses such as agriculture (including oil palm and cattle ranching), mining, or energy infrastructure.
• Urbanization is the long-term, permanent conversion of forests to towns, cities and urban infrastructure such as roads.
• Shifting agriculture is the small to medium-scale conversion of forest for farming, that is later abandoned so that forests regrow. This is common of local, subsistence farming systems where populations will clear forest, use it to grow crops, then move on to another plot of land.
• Forestry production is the logging of managed, planted forests for products such as timber, paper and pulp. These forests are logged periodically and allowed to regrow.
• Wildfires destroy forests temporarily. When the land is not converted to a new use afterwards forests can regrow in the following years.

Thanks to satellite imagery, we can get a birds-eye view of what these drivers look like from above. In the figure we see visual examples from the study of forest loss classification by Philip Curtis et al. (2018), published in Science.²

Commodity-driven deforestation and urbanization are deforestation: the forested land is completely cleared and converted into another land use – a farm, mining site, or city. The change is permanent. There is little forest left. Forestry production and wildfires usually result in forest degradation – the forest experiences short-term disturbance but if left alone is likely to regrow. The change is temporary. This is nearly always true of planted forests in temperate regions – there, planted forests are long-established and do not replace primary existing forests. In the tropics, some forestry production can be classified as deforestation when primary rainforests are cut down to make room for managed tree plantations.³

'Shifting agriculture’ is usually classified as degradation because the land is often abandoned and the forests regrow naturally. But it can bridge between deforestation and degradation depending on the timeframe and permanence of these agricultural practices.

One-quarter of forest loss comes from tropical deforestation

We’ve seen the five key drivers of forest loss. Let’s put some numbers to them.

In their analysis of global forest loss, Philip Curtis and colleagues used satellite images to assess where and why the world lost forests between 2001 and 2015. The breakdown of forest loss globally, and by region, is shown in the chart.²

Just over one-quarter of global forest loss is driven by deforestation. The remaining 73% came from the three drivers of forest degradation: logging of forestry products from plantations (26%); shifting, local agriculture (24%); and wildfires (23%).

We see massive differences in how important each driver is across the world. 95% of the world’s deforestation occurs in the tropics [we look at this breakdown again later]. In Latin America and Southeast Asia in particular, commodity-driven deforestation – mainly the clearance of forests to grow crops such as palm oil and soy, and pasture for beef production – accounts for almost two-thirds of forest loss.

In contrast, most forest degradation – two-thirds of it – occurs in temperate countries. Centuries ago it was mainly temperate regions that were driving global deforestation [we take a look at this longer history of deforestation in a related article]. They cut down their forests and replaced it with agricultural land long ago. But this is no longer the case: forest loss across North America and Europe is now the result of harvesting forestry products from tree plantations, or tree loss in wildfires.

Africa is also different here. Forests are mainly cut and burned to make space for local, subsistence agriculture or for fuelwood for energy. This ‘shifting agriculture’ category can be difficult to allocate between deforestation and degradation: it often requires close monitoring over time to understand how permanent these agricultural practices are.

Africa is also an outlier as a result of how many people still rely on wood as their primary energy source. Noriko Hosonuma et al. (2010) looked at the primary drivers of deforestation and degradation across tropical and subtropical countries specifically.⁴  The breakdown of forest degradation drivers is shown in the following chart. Note that in this study, the category of subsistence agriculture was classified as a deforestation driver, and so is not included. In Latin America and Asia the dominant driver of degradation was logging for products such as timber, paper and pulp – this accounted for more than 70%. Across Africa, fuelwood and charcoal played a much larger role – it accounted for more than half (52%).

This highlights an important point: less than 20% of people in Sub-Saharan Africa have access to clean fuels for cooking, meaning they still rely on wood and charcoal. With increasing development, urbanization and access to other energy resources, Africa will shift from local, subsistence activities into commercial commodity production – both in agricultural products and timber extraction. This follows the classic ‘forest transition’ model with development, which we look at in more detail in a related article.

Tropical deforestation should be our primary concern

The world loses almost six million hectares of forest each year to deforestation. That’s like losing an area the size of Portugal every two years. 95% of this occurs in the tropics. The breakdown of deforestation by region is shown in the chart. 59% occurs in Latin America, with a further 28% from Southeast Asia. In a related article we look in much more detail at what agricultural products, and which countries are driving this.

As we saw previously, this deforestation accounts for around one-quarter of global forest loss. 27% of forest loss results from ‘commodity-driven deforestation’ – cutting down forests to grow crops such as soy, palm oil, cocoa, to raise livestock on pasture, and mining operations. Urbanization, the other driver of deforestation accounts for just 0.6%. It’s the foods and products we buy, not where we live, that has the biggest impact on global land use.

It might seem odd to argue that we should focus our efforts on tackling this quarter of forest loss (rather than the other 73%). But there is good reason to make this our primary concern.

Philipp Curtis and colleagues make this point clear. At their Global Forest Watch platform they were already presenting maps of forest loss across the world. But they wanted to contribute to a more informed discussion about where to focus forest conservation efforts by understanding why forests were being lost. To quote them, they wanted to prevent “a common misperception that any tree cover loss shown on the map represents deforestation”. And to “identify where deforestation is occurring; perhaps as important, show where forest loss is not deforestation”.

Why should we care most about tropical deforestation? There is a geographical argument (why the tropics?) and an argument for why deforestation is worse than degradation.

Tropical forests are home to some of the richest and most diverse ecosystems on the planet. Over half of the world’s species reside in tropical forests.⁵ Endemic species are those which only naturally occur in a single country. Whether we look at the distribution of endemic mammal species, bird species, or amphibian species, the map is the same: subtropical countries are packed with unique wildlife. Habitat loss is the leading driver of global biodiversity loss.⁶ When we cut down rainforests we are destroying the habitats of many unique species, and reshaping these ecosystems permanently. Tropical forests are also large carbon sinks, and can store a lot of carbon per unit area.⁷

Deforestation also results in larger losses of biodiversity and carbon relative to degradation. Degradation drivers, including logging and especially wildfires can definitely have major impacts on forest health: animal populations decline, trees can die, and CO₂ is emitted. But the magnitude of these impacts are often less than the complete conversion of forest. They are smaller, and more temporary. When deforestation happens, almost all of the carbon stored in the trees and vegetation – called the ‘aboveground carbon loss’ –  is lost. Estimates vary, but on average only 10-20% of carbon is lost during logging, and 10-30% from fires.⁸ In a study of logging practices in the Amazon and Congo, forests retained 76% of their carbon stocks shortly after logging.⁹ Logged forests recover their carbon over time, as long as the land is not converted to other uses (which is what happens in the case of deforestation).

Deforestation tends to occur on forests that have been around for centuries, if not millennia. Cutting them down disrupts or destroys established, species-rich ecosystems. The biodiversity of managed tree plantations which are periodically cut, regrown, cut again, then regrown is not the same.

That is why we should be focusing on tropical deforestation. Since agriculture is responsible for 60 to 80% of it, what we eat, where it’s sourced from, and how it is produced is our strongest lever to bring deforestation to an end.

Hannah Ritchie (2021) - “Not all forest loss is equal: what is the difference between deforestation and forest degradation?” Published online at OurWorldinData.org. Retrieved from: 'https://ourworldindata.org/deforestation-degradation' [Online Resource]

@article{owid-deforestation-degradation,
    author = {Hannah Ritchie},
    title = {Not all forest loss is equal: what is the difference between deforestation and forest degradation?},
    journal = {Our World in Data},
    year = {2021},
    note = {https://ourworldindata.org/deforestation-degradation}
}

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