Forest planting is widely promoted as a nature-based solution to climate change. Scientific evidence suggests that afforestation and reforestation can increase soil carbon storage and support microbial life. However, the benefits are not guaranteed to last under every environmental condition.
Rising temperatures and prolonged droughts threaten forests’ ability to absorb carbon, making these connections increasingly under pressure. Biodiversity is declining, ecosystems are deteriorating, and international commitments to protect nature remain inadequately fulfilled.
The central challenge is, therefore, not simply to plant more trees. It is to protect the functioning ecosystems, restore degraded landscapes and preserve the delicate relationships among water, soil, vegetation and biodiversity. Meaningful restoration; therefore, requires coordinated action, sustained investment and approaches that strengthen ecosystems and improve the well-being of the communities that depend on forests.
Forests and Biodiversity Conservation: Forest Restoration Can Rebuild Soil Carbon and Microbial Life
Forests are far more than a collection of trees. Beneath its canopy lies a living world of microorganisms, fungi, roots and soil organisms. Above it, leaves exchange carbon dioxide and water vapour with the atmosphere. Across landscapes, forests influence rainfall, protect habitats and support the ecological processes on which human societies depend. Forests help regulate the carbon cycle by storing carbon in their trunks, branches, leaves, roots and soils.
Their contribution extends below ground, where microorganisms support nutrient cycling and the processes that maintain soil health. A large-scale analysis of 1,158 paired afforestation or reforestation and reference sites across six continents examined how tree planting affects soil carbon storage and microbial biomass over time. The findings indicate that afforestation can support increases in topsoil carbon storage and soil microbial biomass as planted forests develop.
Reforestation can also help previously forested land recover these properties, with soil carbon and microbial biomass approaching levels found in original forests during the first three decades. However, these recovery gains were not consistently sustained in older stands. Responses also varied according to previous land use, climatic conditions and the tree species planted. Degraded lands generally experienced greater improvements. These findings highlight an important distinction: restoring a forest is not merely about establishing tree cover. It is about rebuilding the ecological processes that make a forest function.
Healthy soil contains diverse organisms that break down organic matter, release nutrients and contribute to the formation of stable soil carbon. Protecting this underground life is therefore an essential part of successful restoration. Tree planting can contribute to climate mitigation, but its effectiveness depends on what is planted, where it is planted and how the ecosystem develops over time.
Why Drought Can Turn Forests from Carbon Sinks into Carbon Sources
Forests absorb a substantial share of the carbon dioxide released by human activities. However, their capacity to perform this vital function depends heavily on water availability. During photosynthesis, trees absorb carbon dioxide through tiny pores on their leaves called stomata. They use sunlight to convert carbon dioxide and water into sugars that support growth and metabolism. But these pores also allow water vapour to escape through transpiration.
Under favourable conditions, this exchange supports plant growth and helps transport water from roots to leaves. During drought, the same process becomes dangerous. As soil moisture declines and atmospheric conditions become hotter and drier, trees face a difficult choice: continue opening their stomata to absorb carbon dioxide or close them to conserve water. Trees generally close their stomata during severe water stress. This reduces water loss but also restricts photosynthesis, weakening their ability to absorb carbon dioxide.
Extreme drought can cause an additional problem known as cavitation. Water moves through a tree’s vascular system under tension. When that system fails, air bubbles can form inside water-conducting vessels, obstructing the flow of water. Severe damage can cause leaves and tissues to dry out and, in some cases, lead to tree death. When trees die, some of the carbon stored in their tissues may eventually return to the atmosphere through decomposition or burning.
Meanwhile, living trees and soil organisms continue releasing carbon dioxide through respiration. If photosynthesis declines sufficiently while these emissions continue, a forest ecosystem can temporarily become a net carbon source rather than a carbon sink.
This does not mean every drought makes every forest emit more carbon than it absorbs. The outcome depends on drought severity, duration, forest type and other environmental conditions. Nevertheless, increasingly severe water stress threatens the reliability of forests as long-term carbon stores.
Water, Forests and the Climate Connection
The relationship between forests and climate extends far beyond carbon dioxide. Trees draw water from the soil and release it into the atmosphere through transpiration. This moisture contributes to atmospheric humidity and can help support rainfall downwind.
The Amazon basin provides an important example. Moisture recycled through the rainforest helps sustain rainfall across parts of South America. Changes in forest cover, transpiration and atmospheric circulation can therefore affect water availability far beyond the locations where trees are lost.
Increasing atmospheric carbon dioxide may, under some conditions, allow plants to absorb carbon dioxide while opening their stomata less widely. This can improve water-use efficiency at the leaf level. However, reduced transpiration can also influence the movement of moisture through ecosystems. The overall consequences depend on vegetation, soil moisture, atmospheric circulation and regional climate patterns.
The relationship is complex: forests depend on rainfall, influence water cycling and store carbon, while changing climatic conditions affect all three processes. This interconnectedness explains why forest conservation cannot be separated from water security.
Protecting forests while allowing surrounding landscapes to degrade may not be enough. Sustainable land management, watershed protection and the conservation of natural vegetation are also needed to maintain ecological resilience.
The Sixth Mass Extinction: What Biodiversity Loss Means for People
Forests are only one part of a much larger living system. Biodiversity encompasses the variety of life, from microscopic organisms in the soil and human gut to pollinating insects, birds, large mammals and marine species. Each contributes to ecological processes that support human well-being.
According to the World Wildlife Fund’s Living Planet Report 2024, monitored populations of vertebrate wildlife declined by an average of 73% between 1970 and 2020. The reported decline was particularly severe for monitored freshwater populations.
These figures describe changes in monitored wildlife populations, not the percentage of all individual animals that have disappeared or the proportion of species that have gone extinct. Nevertheless, they reveal the scale of pressure facing many ecosystems.
Scientists warn that human activities are driving an alarming loss of biodiversity. Habitat destruction, intensive agriculture, pollution, overexploitation and climate change are among the major pressures. The phrase sixth mass extinction describes concern that the current rate of species loss could develop into a mass extinction event comparable in scale to major episodes in Earth’s geological history.
For people, the consequences are not confined to wildlife. Biodiversity supports food production, freshwater quality, soil fertility, pollination and the regulation of pests and diseases. When these natural systems weaken, communities may face higher costs, declining harvests and greater vulnerability to environmental shocks. Nature’s contribution is often most visible when it disappears.
Wetlands and the cost of losing natural protection
Wetlands demonstrate how ecosystem degradation can create direct economic consequences. Marshes and swamps can filter water, retain sediments and help remove excess nutrients. When these habitats disappear, pollutants may move more readily into rivers, lakes and other water supplies.
Communities may then need more expensive treatment systems to provide safe drinking water. Wetlands also provide habitats for fish, birds, amphibians and countless smaller organisms. Their loss can damage fisheries, reduce biodiversity and weaken natural protection against floods. Protecting wetlands is therefore not simply a conservation preference. It is an investment in water quality, public well-being and ecological stability.
Pollinators, food security and medicine
Bees, bats and other pollinators contribute to the reproduction of many flowering plants and food crops. More than three-quarters of global food crop types benefit from animal pollination to some degree, although their dependence varies. The loss of pollinators can threaten crop quality, yields and the diversity of foods available to people. Biodiversity also provides valuable resources for medicine.
Many medicines originate from natural compounds or were developed by studying biological processes. Penicillin, for example, emerged from research involving a mould, while numerous other treatments have been developed using compounds found in plants, fungi and other organisms.
When species disappear, humanity may lose biological resources that could have helped researchers develop future treatments. The loss is therefore not only ecological. It can also diminish future scientific opportunities.
Why Every Species Can Matter
Nature is sometimes described as a team in which every player has a role. The analogy is useful because species do not exist in isolation. Some organisms perform functions that others can partly replace. But certain species have such strong effects on their surroundings that their disappearance can trigger major changes throughout an ecosystem. These are known as keystone species.
Oysters, for example, can filter water as they feed and can form reefs that provide shelter for other organisms. The decline of oyster reefs can therefore affect water quality, marine habitats and local biodiversity. Similarly, pollinating insects help plants reproduce, soil microorganisms regulate nutrient availability, and predators can influence the abundance and behaviour of other animals.
The precise consequences of losing a species depend on its ecological role and the wider condition of the ecosystem. Yet the broader lesson remains clear: a diverse natural community is often better equipped to sustain essential ecological functions than a severely degraded one. Conserving biodiversity means protecting the relationships that connect species, not merely counting how many remain.
COP17 and the Challenge of Turning Promises into Action
The global biodiversity crisis has prompted governments to adopt international commitments, but implementation remains a major challenge. The 17th Conference of the Parties to the Convention on Biological Diversity, known as COP17, opened in Yerevan, Armenia, on October 19, 2026. The meeting represents a halfway checkpoint for the Kunming-Montreal Global Biodiversity Framework, adopted in 2022.
The framework contains 23 targets for 2030. Among its ambitions are conserving at least 30% of the world’s land, inland waters and marine and coastal areas, restoring degraded ecosystems, reducing pollution and mobilising greater financial resources for biodiversity.
A global progress report released ahead of COP17 indicated that fewer than half of the assessed biodiversity targets were on track. This shortfall raises difficult questions about political commitment, financial support and the gap between international promises and environmental outcomes.
Delegates are working towards the Yerevan Pathway, intended to accelerate implementation and address gaps in biodiversity finance and action. The challenge is substantial. Protected areas must be effectively managed, restoration must deliver genuine ecological benefits, and Indigenous Peoples and local communities must have meaningful opportunities to participate in decisions affecting their lands and livelihoods.
Governments must also address contradictions between conservation commitments and decisions that permit environmentally damaging activities. International agreements can establish common goals, but their value ultimately depends on implementation, transparent monitoring and accountability. The future of biodiversity will be shaped less by the number of promises announced at conferences than by what happens on the ground.
From Tree Planting to Ecosystem Protection
The evidence from forest research, drought science and biodiversity assessments points towards a broader approach to environmental protection. Planting trees is useful, particularly where it restores degraded land and rebuilds native forest ecosystems. But tree planting is not a substitute for protecting existing natural forests, wetlands, grasslands and other valuable habitats. Successful restoration should consider several interconnected priorities.
Protect existing natural ecosystems. Mature forests and other intact habitats contain complex ecological relationships that can take decades or centuries to develop. Preventing their destruction should remain a priority.
Restore degraded land appropriately. Native species and locally suitable mixtures can help rebuild habitats and improve soil conditions. Restoration plans should reflect local ecology rather than rely on a single planting formula.
Protect soil health. Organic matter, soil organisms and nutrient cycling are essential for ecosystem recovery. Land management should avoid unnecessary soil disturbance and degradation.
Strengthen water security. Forest protection should be integrated with watershed management, wetland conservation and measures that maintain soil moisture and natural water flows.
Prepare forests for drought. Conservation and restoration strategies should account for local climatic conditions, water availability, species characteristics and the risks of extreme heat.
Measure long-term outcomes. The success of a project should be assessed through more than the number of seedlings planted. Tree survival, biodiversity, soil carbon, water conditions and ecosystem resilience also matter.
Make governments accountable. International biodiversity targets require sufficient funding, credible reporting and policies that align development decisions with ecological protection. These priorities recognise that a forest is a living system, not simply a carbon-storage project.
Conclusion: Protecting Nature Means Protecting Our Future
The climate crisis and the biodiversity crisis are deeply connected. Forests absorb carbon, soils support microbial life, water sustains vegetation, and biodiversity maintains the ecological processes that make human life possible.
Yet these benefits cannot be taken for granted. Drought can weaken forest carbon uptake, damaged soils can undermine restoration, and the disappearance of species can disrupt the natural systems that provide food, clean water and other essential resources.
Scientific research offers grounds for hope: restoring degraded forests can rebuild important soil properties, and protecting biodiversity can help maintain the systems on which societies depend. But the results require sustained effort, informed planning and long-term protection.
COP17 provides an opportunity to translate international commitments into measurable progress. Its significance will ultimately depend on whether governments close the implementation gap and support meaningful conservation on the ground.
The lesson is simple but profound: nature-based climate solutions work best when we protect the whole ecosystem, not just the trees. A planted forest needs water. Healthy soil needs living organisms. Wildlife needs connected habitats. And human societies need all these systems to remain resilient. Protecting nature is therefore not a choice between climate action and biodiversity conservation. It is a shared responsibility to preserve the foundations of life on Earth.
References
Bai, Y., Cotrufo, M. F., et al. “Afforestation and Reforestation Affect Soil Carbon and Microbial Biomass Globally.” Nature Communications.
Intergovernmental Panel on Climate Change. Climate Change 2021: The Physical Science Basis. Cambridge University Press, 2021.
Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Global Assessment Report on Biodiversity and Ecosystem Services. IPBES, 2019.
Convention on Biological Diversity. Kunming-Montreal Global Biodiversity Framework. United Nations Environment Programme, 2022.
World Wildlife Fund. Living Planet Report 2024: A System in Peril. WWF, 2024.
Food and Agriculture Organization of the United Nations. The State of the World’s Forests 2024. FAO, 2024.
Millennium Ecosystem Assessment. Ecosystems and Human Well-Being: Wetlands and Water Synthesis. World Resources Institute, 2005.
Intergovernmental Panel on Climate Change. Climate Change 2022: Impacts, Adaptation and Vulnerability. Cambridge University Press, 2022.
Díaz, S., Settele, J., Brondízio, E. S., et al. “Pervasive Human-Driven Decline of Life on Earth Points to the Need for Transformative Change.” Science, vol. 366, no. 6471, 2019.
Potts, S. G., Biesmeijer, J. C., Kremen, C., Neumann, P., Schweiger, O., and Kunin, W. E. “Global Pollinator Declines: Trends, Impacts and Drivers.” Trends in Ecology & Evolution, vol. 25, no. 6, 2010.
