Reforestation
Reforestation: how restoring forests can protect the climate and biodiversity
Desertification, or the loss of fertile and productive soil, is one of the issues exacerbating climate change – as the number of trees decreases, the greenhouse effect increases. One solution is reforestation. Despite its challenges, it has become an alternative for restoring thousands of hectares of land to their former green state.
Without forests, life on Earth would not be possible. Together with the oceans, they are the planet’s lungs and their role in tackling climate change is vital, as they absorb around two billion tonnes of CO₂ every year – the main greenhouse gas and one of the biggest contributors to global warming. The importance and value of these terrestrial ecosystems is undeniable, which is why their protection and conservation form part of the Sustainable Development Goals (SDGs). Specifically, SDG 15: Life on Land seeks to protect, restore and promote the sustainable use of terrestrial ecosystems.
Almost one-third of the planet is covered by forests, equivalent to 4.14 billion hectares. These vast areas of woodland provide us with the essentials for survival: the water we drink, the food we eat and the air we breathe. However, we are destroying our source of life: it is estimated that human activity eliminated 10.9 million hectares of forest every year between 2015 and 2025, a figure that represents a positive sign compared with previous periods, when this rate was higher.
According to the Global Forest Resources Assessment 2025 report by the Food and Agriculture Organization of the United Nations (FAO), an estimated 489 million hectares of forest – an area larger than the European Union – have been lost worldwide since 1990. Although this gradual loss has slowed in recent years, forests are not recovering at a sufficient rate. In fact, between 2015 and 2025, the rate of reforestation fell by almost three million hectares, from 9.88 million hectares per year in the previous period to 6.78 million.
The overexploitation of natural resources through logging or urban expansion is the main human-driven cause of desertification, but there are also causes beyond human control. These include irregular rainfall and seasonal droughts, soil erosion and poor soils, as well as forest fires caused by climate change. Against this backdrop, reforestation has emerged as one of the most effective strategies for reversing this problem.
What is reforestation. Goals and benefits
Reforestation involves repopulating deforested areas to restore forests that were destroyed in the recent past. Given the loss of large forest areas, which are essential for absorbing CO₂, generating oxygen and combating climate change, large-scale tree planting is needed to prevent ecosystem loss and slow the deterioration of the planet.
Differences between reforestation, afforestation and ecological restoration
Within forestry, the discipline that studies the management of forests and woodland, three possible ways of intervening in natural environments to restore them are distinguished:
- Afforestation: consists of planting trees on land that has never previously been forested.
- Reforestation: involves replanting trees in areas that were once forested but where forests have been lost. These may be native species or other species selected for their rapid growth.
- Ecological restoration: in this case, the aim is to recover an entire ecosystem (soil, fauna, flora and functions), not just trees.
SEE INFOGRAPHIC: Why is it important to take care of forests? [PDF] External link, opens in new window.
Reforestation, therefore, is a way of achieving an array of objectives, all of which seek to restore the stability offered by forests:
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Restoring biodiversity loss
Forests are home to more than 80% of all terrestrial species worldwide. Specifically, according to The State of the World’s Forests 2025 (FAO), there are more than 58,000 tree species worldwide. Forests provide habitats for 80% of amphibians, 75% of birds and 68% of mammals, according to the latest data published in its 2020 report. Their degradation and disappearance are driving hundreds of species towards extinction despite conservation efforts. The European Union's Biodiversity Strategy for 2030 includes the planting of at least three billion trees across Europe to help protect biodiversity.
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Reducing carbon dioxide in the atmosphere
Human activity causes annual emissions of around 40 Gt of CO₂. Half of these gases remain in the atmosphere, contributing to global warming, while the other half is absorbed by forests and oceans. Reforestation is essential for our own survival: forests are vital carbon sinks that help slow climate change. Without them, the planet’s average temperature will continue to rise, causing further impacts such as rising sea levels and the melting of glaciers and polar ice.
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Reversing soil erosion and restoring watersheds
Forest trees protect soil from erosion by reducing the impact of wind and rainfall. Eroded and infertile soils harm agriculture and increase the risk of landslides and flash floods. Reforestation seeks to mitigate this situation, which is also intensified by indiscriminate logging, preserving soil fertility through firmly established root systems. At the same time, watersheds recover as nutrients are restored.
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Protecting human health
The degradation of different habitats can also contribute to an increase in the transmission of emerging infectious diseases. Around 75% of these diseases, such as avian influenza and Ebola, are transmitted from wildlife to humans. Forest degradation, without effective reforestation, increases human exposure to zoonotic diseases.
Types of reforestation
Depending on the area replanted, there are two types of reforestation:
- Urban reforestation. This is tree planting in developed areas. The purpose depends on the city's needs: modify the climate — green zones are good for beating the heat —, improve air quality — heavy traffic in cities increases CO2 levels — provide more shady areas or enhance the appearance of the environment.
- Rural reforestation. Huge numbers of trees are planted in areas that have suffered deforestation, places which were once forests, jungles or covered with semi-arid vegetation. Forests can also be planted in areas where they have never existed, although the correct term in this case would be forestation. There are different subtypes within reforestation depending on the intention. Conservation, protection and restoration, agro-forestry and productive.
When a reforestation plan is carried out properly, it also becomes a powerful nature-based decarbonisation solution. In addition to the direct impact forests have on local flora and fauna, they become an essential tool for controlling CO₂ emissions. Through our Carbon2Nature initiative, we are launching innovative projects around the world that protect biodiversity while tackling the impact of excess greenhouse gases.
How reforestation is carried out
To reforest land left barren due to indiscriminate logging, fires or deforestation caused by climate change, a plan must be developed. Reforestation must be sustainable, meaning it is not simply a matter of planting trees arbitrarily. The main issues to consider are:
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Conducting a field study
First, the land must be analysed and the conditions of the site assessed: from the soil – depth, texture and fertility – to the climate – dry or wet seasons (humidity is essential) – and the types of populations inhabiting the ecosystem – native fauna and flora.
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Selecting species for repopulation
The best option is usually to choose native species, although imported fast-growing species that are compatible with the soil and climate may also be included. Forest genetic material must be of good quality and ideally the nursery of origin should be located no more than 100 kilometres away. The method and timing of transport are also important, avoiding direct sunlight and strong winds.
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Choosing a planting method
The land must be prepared, appropriate tools selected and the least invasive technique chosen. In addition, the height and coverage of each new plant must be considered to ensure they do not compete with one another. Planting does not end once the forest genetic material has been introduced; a monitoring plan must also be implemented.
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Establishing a protection plan
As part of the monitoring plan, measures must be developed to protect the restored forest from potential diseases, pests, fires and illegal logging, among other threats. Maintenance and assessments are essential to consolidate reforestation efforts.
Mistakes to avoid in a reforestation plan
According to the Global Forest Resources Assessment 2025 (FAO), more than 2.13 billion hectares of forest worldwide have management plans. Developing guidelines for the proper functioning of forests is an essential starting point when restoring a forest or launching a reforestation project because, as with any process, problems can arise:
- If reforestation is impulsive, meaning it does not have a sound implementation plan, it can be counterproductive, damaging species diversity or agricultural crops.
- Large-scale forest plantations can have the opposite effect to that intended, drying out and impoverishing soils due to excessive salt concentration.
- Poor selection of tree species, as well as inadequate planting methods and positioning, can be harmful. In addition, introducing invasive species can contribute to the extinction of others.
- Poorly planned reforestation can result in monocultures, which not only affect native plant diversity but also the habitats of different forest species.
Strategic reforestation to maximise its impact
Restoring forest areas is a delicate task, with many factors that must be considered before starting any project. Understanding the potential impact of a reforestation plan in advance represents a major step forward in ensuring appropriate environmental protection. With this aim, a study led by scientists from The Nature Conservancy (TNC) and published in Nature Communications proposed a more realistic approach to global reforestation, reducing previous estimates of land suitable for tree planting.
By combining data from 89 studies on the subject, researchers developed a tool that identifies which areas are suitable for successful reforestation. It considers both soil suitability and the protection of other priority uses, including habitat conservation, food production and regional freshwater availability. It also takes into account albedo, a phenomenon through which the development of wooded areas can have counterproductive effects by changing the amount of sunlight reflected or absorbed, as well as native grasslands, which are essential for local wildlife.
The study identified 195 million hectares where reforestation can provide maximum climate benefits while generating the least conflict with food production and territorial rights. The aim is to reduce failed interventions that could become counterproductive and make the best possible use of resources dedicated to these objectives, ensuring conservation efforts are more effective.
Ultimately, reforestation is not only about planting more trees, but also about doing so better. Through good planning, it is possible to restore lost green areas, support or rehabilitate regional biodiversity and absorb CO₂ from the atmosphere to protect the environment.