Forest loss has halved in the past 30 years, latest global update shows

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Between 1990 and 2015, global forest area declined by 3%, but the rate of loss has halved between the 1990s and the past five years. Most of this loss occurs in the tropics.

Forests are a big deal. They provide us with clean water, they sequester and store carbon, they provide timber and non-timber forest products, and are vital to the everyday survival of many of the world's poorest people, who live in and around forests.

They also provide valuable habitat for animal and plants species. For example, tropical forests, while covering only 15% of the global land area, contain over 50% of land animals and plants.

The area of land covered by forest and trees is therefore an important indicator of global environmental condition. Every five years, the Food and Agriculture Organisation of the United Nations produces results from its Global Forest Resources Assessment. This assessment involves a major survey of all countries using a common reporting framework, agreed definitions and reporting standards to provide statistics on forest area and related data on forest condition and use.

The assessment is the most comprehensive global picture of forests. The data collection involves hundreds of scientists and technical experts from across the world.

The 2015 results were released this week at the World Forestry Congress in Durban, South Africa. With a team of co-authors over the past year, I have worked with the Food and Agriculture Organisation to analyse data on forest area and area change, comparing climatic domains (tropical, sub-tropical, temperate and boreal), geographical regions and country income categories. This study has recently been published.

Our results showed that total forest area declined by 3% between 1990 and 2015, from 4,128 million hectares to 3,999 million ha. The good news is that the annual rate of net forest loss halved from 7.3 million ha per year in the 1990s to 3.3 million ha per year between 2010 and 2015.

Natural forest loss between 1990 and 2015 was higher, declining by 6%, from 3,961 million ha to 3,721 million ha, while planted forest (including rubber plantations) increased from 168 million ha to 278 million ha.

Where are forests disappearing?

There was a significant difference in net forest loss between climatic domains, with most deforestation occurring in the tropics. From 2010 to 2015, tropical forest area declined by 5.5 million ha per year while temperate forest area expanded at a rate of 2.2 million ha per year. Boreal and subtropical forest areas showed little net change.

Forest area declined in Central and South America, in South and Southeast Asia and all three regions in Africa. Forests expanded in Europe, North America, the Caribbean, East Asia and Western-Central Asia.

Brazil (984,000 ha per year), Indonesia (684,000 ha per year) and Nigeria (410,000 ha per year) had the largest net forest loss between 2010 and 2015. For Brazil and Indonesia, these rates of forest loss were significantly lower than in the 1990s.

Countries reporting a large forest expansion from 2010 to 2015 included China (1.5 million ha per year), Chile (301,000 ha per year) and the USA (275,000 ha per year).

The assessment does not provide data on the drivers of forest loss. Other studies show that major drivers are large and small-scale agriculture, urban expansion and clearance for infrastructure, such as roads, mines and hydro-electric dams.

We can see from our study that loss is occurring most rapidly in some of the poorest countries. The concept "forest transitions" has been identified in studies of forest change and economic development. Over the course of a country's economic development the dynamics of forest area generally follows a U shape.

Poorer countries undergo significant forest loss then, as the economy develops, forest cover increases. Our analysis indicates that, between 1990 and 2015, 13 tropical countries may have either passed through their forest transitions from net forest loss to net forest expansion, or continued along the path of forest expansion that follows these transitions. These include India, Vietnam, Ghana, Laos and Costa Rica.

Building a complete picture

The assessment differs from other global or tropical assessments that rely only on remotely sensed data to assess change in forest area. Remote sensing studies detect changes in tree cover, but do not discriminate between forest areas that are disturbed, for example by timber harvesting, fire or insect pests and will regenerate and remain forests, and areas of forest that are permanently converted to other land uses.

Consequently, studies like the World Resources Institute's Global Forest Watch report large areas of tree cover loss in places like Russia, Canada and the United States, while the Global Forest Resource Assessment reports either expansion or little change in forest area in these countries.

Comparing the 2015 assessment data to these remote sensing surveys was therefore challenging, due to these different definitions of forest, differences in the assessment periods and in assessment methods. Overall, when similar definitions are applied (such as the threshold tree cover for vegetation to be considered forest) the findings of our 2015 assessment are consistent with these other studies.

While most developed countries have had high-quality forest monitoring for some time, forest data from many developing countries has often been out of date or incomplete. Data quality is improving in many tropical developing countries with high forest cover, in part because of investment to support the implementation of the REDD+ mechanism under the UN Climate Change Convention.

However, some countries, such as the Democratic Republic of Congo, Angola and Bolivia, are reporting significant forest areas but based on low-quality data. More investment in national and global forest monitoring is therefore needed to improve our understanding of forest dynamics.

With a large forest area and a small population, Australia has also been challenged in forest monitoring. Our reported area of forest has varied between 164 million ha in 2003 and 125 million ha in 2013, with the reduced area primarily the results of better quality forest mapping in remote regions of northern Australia. Based on these new estimates, Australia reported that our forest area declined from 128.5 million ha in 1990 to 124.7 million ha in 2015, but with a net gain of 1.5 million ha between 2010 and 2015.

The 2015 assessment also includes data on forest ecosystem condition and productivity, carbon stocks, sustainable forest management, designation for different uses and economic and social benefits of forests. As we move towards the UN climate change meeting in Paris and the agreement of a new set of Sustainable Development Goals, the value of forests in addressing climate change and other global and national development objectives is becoming more apparent.