How Do Forests Affect Climate?

The question of how do forests affect climate is a nuanced one influenced by a number of factors.

Forests play a critical role in the carbon cycle due to their high sequestration capabilities¹. They also help in regulating surface temperatures – something that is often overlooked².

Through vegetation, plant biomass, wood, trees, and organic soils, forests play a key role in regulating the climate. The IPCC (The Intergovernmental Panel on Climate Change) has identified them as a key factor in climate change mitigation efforts³, and understanding what they do helps to see why.

Forests, Carbon Sinks, and the Climate

Firstly, forests act as carbon sinks. A carbon sink is a reservoir that can absorb and store the atmosphere’s carbon by using biological mechanisms. Forests store carbon as biomass in trunks, branches, foliage, roots, and soils. However, it does not end there. They absorb carbon dioxide during the process of photosynthesis, which reintroduces oxygen into the atmosphere⁴.

However, the ability of forests to act as carbon sinks is no longer safe in the long term. Tropical forests are removing less carbon dioxide from the atmosphere as a result of deforestation, reducing their ability to act as carbon sinks. Instead, forests like the Amazon could turn into a source of carbon in the next decade. This is due to the damage caused by loggers, farming interests⁵ and the impacts of the climate crisis, new research has found⁶. The ability of forests to act as carbon sinks is under threat from other climate impacts such as droughts. Evidence of this can be seen in Borneo⁷.

Forests, the Albedo Effect, and the Climate

Secondly, forests can have an albedo effect on the environment⁸. An albedo effect refers to the amount of incoming solar radiation that is reflected by an object. Objects that are dark in color typically absorb heat, whereas lighter objects reflect heat while reducing surface temperature.

Therefore, the dark green forest cover has a low albedo and absorbs more sunlight. Research is currently looking into how large the albedo effect is on the Earth’s climate. In the northern forests, the seasonality of albedo is largely due to the snow cover which can shift the albedo from 7% to 80%⁹. This shows how location and seasonality are also factors in how forests affect the climate.

How Do Forests Fit into Mitigation Efforts?

The IPCC¹⁰ recognizes the role forests play in mitigation efforts. They outline several ways that the forest has the potential to help offset the effects of climate change. For example, reforestation and maintenance is a way of preventing the loss of carbon sinks. The halting of forest loss and promotion of restoration is needed to meet the Paris Climate Agreement¹¹. If we do this, forests have the potential to contribute to over one-third of the total climate change mitigation required by 2030, according to scientists¹².

Reforestation and the planting of new forests are cost-effective ways to mitigate the impacts of climate change, according to studies¹³. This is why several countries are exploring these methods to help meet climate goals. The low costs associated with afforestation are lower than other carbon removal technologies (e.g. bioenergy with carbon capture and storage) making them much more attractive¹⁴.

However, large-scale afforestation is hard to implement globally. Its effectiveness differs depending on the location, making its application unfavorable in some regions. Expansion of forests in the tropics results in cooling, while afforestation in the boreal zone might have a limited effect or might even result in warming, according to research ¹⁵ using earth system models.

In conclusion

The issue to ensure global 2030 climate goals are met ¹⁶. It must also be considered that felling large trees to allow smaller ones to grow back is not a good ecological approach. It will release more of the carbon that was stored in fossil fuels and roots into the atmosphere. It is therefore important to protect existing forests rather than focusing on planting new trees.

References 

1. Forests play a key role in the global carbon cycle and climate change, Michigan State University, 3 May 2012
2. Deforestation in Brazil could significantly increase local surface temperatures, Newscenter, 20 March 2019
3. Landmark IPCC report urges world to halt deforestation, Environmental Investigation Agency, 9 August 2019
4. What IS Photosynthesis? Live Science, 15 October 2018
5. Why is the Amazon Rain Forest Disappearing? Time, date unknown
6. Asynchronous carbon sink saturation in African and Amazonian tropical forests, Nature, 4 March 2020
7. Long-term carbon sink in Borneo’s forests halted by drought and vulnerable to edge effects, Nature Communications, 2017
8. “Albedo effect” in forests can cause added warming, bonus cooling, Oregon State University, 19 October 2011
9. Albedo matters for the climate, and forestry can have an impact on it, Phys.org, 4 December 2019
10. Special Report on Climate Change and Land; Summary For Policymakers, IPCC
11. New research shows why forests are absolutely essential to meeting Paris Climate Agreement goals, Mongabay, 9 November 2017
12. Issues brief: Forests and climate change, International Union for Conservation of Nature (IUCN)
13. Afforestation for climate change mitigation: Potentials, risks and trade‐offs, Jonathan C. Doelman, 26 October 2019
14. Plant trees to mitigate climate change, urge scientists, European Scientist, 6 July 2019
15. Afforestation to mitigate climate change: impacts on food prices under consideration of albedo effects, Ulrich Kreidenweis, 27 July 2016
16. United Nations strategic plan for forests, 2017-2030, United Nations