Saturday, May 25, 2019

Trees and Forests: There is Good News and Bad News

Although the enthusiasm for planting trees is well warranted, they are not a panacea. Forests provide a wide range of benefits but humans are making it very hard for them to provide their vast array of benefits.

Trees are an important part of combating the climate crisis. Forests can sequester up to a third of the 30 to 40 billion tons of climate change causing carbon dioxide we emit each year. However, no matter how many trees we plant there will never be enough to keep temperatures from exceeding the upper threshold limit. As reported in a Business Insider article by Rob Ludacer and Jessica Orwig, "there isn't enough space on Earth to plant the amount of trees it would take to prevent the climate from warming by 3.6 degrees Fahrenheit." Even if trees covered the entire contiguous US they would only sequester about 10 percent of the country's annual CO2 emissions.

We are planting trees on a vast scale. However much of the trees being planted are massive monoculture farms which are nowhere near as effective in sequestering carbon as natural forests. Research by scientists from University College London and University of Edinburgh published as a comment piece in Nature which indicated that 45 percent of the areas countries have pledged to grow trees are commercial plantations.

Although trees combat climate change, they are also being adversely impacted by it. Forests are being hurt by climate related wildfires, insect infestations and pollution. Trees also provide oxygen, however a 2017 study warned that tropical forests are now emitting more carbon than oxygen.

Trees clean the air, but there are limits. We currently emit far more fine particulate matter than trees can absorb. Trees mitigate flooding, but they will not be able to prevent the two meter sea level rise that is predicted by 2100.

Humans are by far the biggest impediment to trees. Humans are destroying the world's most important forests. Some of the world's most ecologically significant forests are being cut down. China is laying waste to the world's second largest rainforest in Central Africa’s Congo Basin to make cheap furniture destined for the United States. The largest rainforest is also under threat from the Bolsonaro government in Brazil. Canada is the world leader in deforestation this includes boreal forest which contain 300 billion tons of stored carbon (soils, plants, and wetlands). These forests are being cut down to make toilet paper destined for the US and native trees are being cut down on Canada's west coast only to find themselves in landfills were the wood breaks down and releases carbon back into the atmosphere. 

Trees cool urban environments but the most recent research suggests you will need to see almost half of a city block covered in tree foliage to make a difference. Trees have also been found to elevate moods, but they cannot insulate people against the grief and anxiety associated with the climate crisis, biodiversity loss and environmental degradation.

Related
The Forest Through the Trees: The Failure of the Ecosystem Services Model
Our Forests are Being Decimated but they can be Reborn
The Vital Role of Forests: Carbon, Rain and Food
The Economic and Employment Benefits of Forests

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