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Are forests the answer to halting global warming and the spread of disease?

Are forests the answer for limiting carbon emissions? That depends on who you ask! Studies of agroforestry and commercial tree plantations aim to find the answer.

Depending on the study you read at any given time, the relationship between malaria and deforestation in the Amazon may be portrayed differently. Some studies claim deforestation decreases the number of malaria infections while others claim the risk of transmission increases where deforestation has occurred1. Like the flu, malaria has seasons of high and low transmission rates. Rainfall and dry season lengths determined survival rates of the main carrier of malaria, the mosquito Nyssorhynchus darlingi1. Deforestation and the creation of agricultural pastures are often associated with the creation of suitable Nydarlingi larval habitat. Fragmentation of forests creates more forest edges where streams and creeks are exposed to partial sunlight. When edges of forest patches are further apart, creeks and streams remain shaded and decrease the abundance of Nydarlingi.

Why does deforestation occur in Brazil?

According to data from the Brazilian Institute of Geography and Statistics (IBGE), Brazil exported enough forestry products and other natural resources to increase the country’s Gross Domestic Product (GDP) by $1.5 billion dollars in 2015. These exports included 26 million tons of firewood, 12 million tons of logs, and 331 thousand tons of wood charcoal3. The largest area of continuous tropical rain forest is in the Amazon and has fallen victim to exploitation. The Brazilian economy has been dependent upon this exploitation and export of natural resources. Trees, such as mahogany, have a high commercial value worldwide and are a motivational factor in illegal logging practices3. Once trees are cleared, the land is transitioned into agricultural pastures.

Can enough forest area be created fast enough?

Although the earth’s forest areas are decreasing, satellite images have shown an increase in overall greenness. Researchers have been able to compare satellite images taken since the 1980s and have determined that agriculture is responsible for a 60% increase in green leaf cover2. Croplands and pastures have minimal impact on carbon storage when compared to forests. Proper forest restoration could limit global warming to 1.5 °C and maintain current green leaf cover worldwide3. In order to achieve this, the Intergovernmental Panel on Climate Change (IPCC) has suggested increasing the world’s forests, woodlands, and woody savannahs by 24 million hectares (Mha) each year through the year 2030. The additional forested areas would then be responsible for sequestering approximately one-third of current atmospheric carbon levels3.

In an effort to reach and surpass the IPCC’s suggested forest cover, the German government and the International Union for Conservation Nature launched the Bonn Challenge in 2011. The challenge aimed to restore an average of 350 Mha of forest by the year 2030. An additional 30Mha of the increased forest area has been committed to restoration by 43 countries. These countries include Brazil, India, and China3.

How can forest cover be increased, rapidly?

In order to achieve a rapid increase in forest cover, nations are taking three main approaches. Abandoned agricultural lands will be left to return to nature, agriculture lands will be transitioned into commercial tree plantations and others will transition into agroforestry.

While this looks like a promising solution, it turns out to be quite the opposite. Commercial tree plantations will be responsible for creating nearly one-half of restored forest cover. Every 10-20 years, these plantations are harvested and cleared, releasing stored CO2 back into the atmosphere3.

The final hurdle

The protection of our forests affects all living things. The leaves of trees mitigate atmospheric carbon dioxide by absorption. The tree cover reduces ideal breeding grounds for malaria and other disease-carrying insects. Commercial tree plantations are only a band-aid for the problem, a temporary fix. Once the science is turned into policy, the only hurdle remaining is how to address the issues surrounding illegal logging operations.

References
1. Chaves, L. S., Conn, J. E., López, R. V., & Sallum, M. A. (2018). Abundance of impacted forest patches less than 5 km2 is a key driver of the incidence of malaria in Amazonian Brazil. Scientific Reports8(1). doi:10.1038/s41598-018-25344-5
2. Chen, C., Park, T., Wang, X., Piao, S., Xu, B., Chaturvedi, R. K., … Myneni, R. B. (2019). China and India lead in greening of the world through land-use management. Nature Sustainability2(2), 122-129. doi:10.1038/s41893-019-0220-7
3. Lewis, S. L., Wheeler, C. E., Mitchard, E. T., & Koch, A. (2019). Restoring natural forests is the best way to remove atmospheric carbon. Nature568(7750), 25-28. doi:10.1038/d41586-019-01026-8
Are forests the answer for limiting carbon emissions? That depends on who you ask! Studies of agroforestry and commercial tree plantations aim to find the answer.
Are forests the answer for limiting carbon emissions? That depends on who you ask! Studies of agroforestry and commercial tree plantations aim to find the answer.

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