Higher incomes, not higher carbon dioxide levels, drive forest gains, study finds

Rising concentrations of climate-altering carbon dioxide in the atmosphere have little to do with surging forest cover in some countries, according to a new study.

“Weather observations confirm indisputably that global temperatures are rising together with atmospheric [carbon dioxide] levels,” Antti Lipponen, a meteorological researcher at the Finnish Meteorological Institute, said in a statement. “However, the study shows that, over more than a century, changes in forest growing stock around the world have been virtually unrelated to those trends.”

Several climate models that scientists use to understand the impact of carbon emissions from sources such as the burning of fossil fuels and widespread deforestation have linked changes in atmospheric chemistry with bumps in tree growth. Higher levels of carbon in the air act as a fertilizer for plants, causing them to grow faster, so the hypothesis goes.

But other data tell a different story. For example, certain countries started having greener forests in the 19th century, before the onset of widespread carbon emissions from human activity. When Lipponen and her colleagues set out to understand why that was, they found that a resurgence in forest cover typically happens as a country becomes more prosperous and its people transition to more efficient forms of agriculture on better farmland.

What’s more, “Developed countries invest in sustainable programs of forest management and nature protection,” the authors write. They published their research on May 14 in PLOS ONE.

Their analyses of forest stocks in countries and whether they are going up or down, alongside measures of income from the World Bank and development from the United Nations Human Development Index, revealed that most places lose forest until they reach a certain income level. The team figures that this threshold at which countries will begin to start gaining forest is around a gross domestic product per person of $20,000 — almost four-and-a-half times previous estimates.

“Human development can translate into the well-being of forest ecosystems,” Lipponen said. “This promotes carbon sequestration and preservation of the global biodiversity in the long term.”

Transitions to increasing forest cover turned up first in places like parts of Europe, the United States, Japan and New Zealand, and more recently in countries with growing economies such as Chile and China.

“Where people and nations are or become relatively well off, we can count on forests absorbing carbon at increasing levels,” Pekka Kauppi, an environmental scientist at the University of Helsinki and the study’s lead author, said in the statement.

But several countries, such as Brazil, Indonesia and Nigeria, which the researchers calculated are losing the most forest, have yet to halt net forest destruction and make the switch to gaining forest.

Understanding the role that development plays in the health of forests could prove helpful in tackling the interconnected problems of climate change and poverty, the authors say.

“Policy analyses must expand from focusing on individual projects such as carbon capture, biodiversity conservation or farm management to inter-disciplinary analyses of harmonized well-being of people and forests,” Lipponen said.

Banner image of deforestation in Indonesia by Rhett A. Butler/Mongabay.

Citation

Kauppi, P. E., Sandström, V., & Lipponen, A. (2018). Forest resources of nations in relation to human well-being. PLOS ONE, 13(5), e0196248.

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