Trees are Facing Unprecedented Die-Offs

Scott Deshefy


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April 29th marked the 150th anniversary of Arbor Day, and never has planting and preserving trees been more crucial. Photosynthesis in forests, the “lungs” of the planet, plays a major role in large-scale production of oxygen from CO2, without which we aerobic forms of life wouldn’t survive. Forests also take greenhouse gases’ carbon out of the atmosphere, slowing anthropogenic climate change from global warming by sequestering that carbon in their biomass. Additionally, forests and oceanic phytoplankton convert sunlight into chemical energy accessible to us animals. Via photosynthesis, solar energy absorbed by the pigment chlorophyll generates glucose (C6H12O6) in the plants we eat. We then consume that energy, either directly or indirectly, as it passes along food chains. When we eat, we’re essentially eating the sun thanks to photosynthetic organisms providing this initial conversion, the predominant transformation on which life forms depend. Forests also help recycle water and regulate rainfall, provide niche-rich habitats for biodiversity, enrich and retain soils, and even provide psychological benefits, what E.O. Wilson describes as “biophilia.” Cutting forests at the rates we are, starting cascades of negative consequences, not only cuts our own throats, but puts the entire biosphere in serious jeopardy.

About one-third of Earth’s land surface, over 15 million square miles, is forested, combining with other vegetation to absorb roughly a third of the carbon dioxide released from burning fossil fuels. Although malaria, Dengue and Yellow Fever and other insect-borne diseases limited human exploitation of rainforests for centuries, Earth has lost a third of its forests in 10,000 years. Since 1900, logging, agriculture and cattle ranching have accounted for half that deforestation. Droughts, wildfires and infestations, worsened by climate change, spread the destruction further. Trees are facing unprecedented die-offs from more frequent and severe stressors including heat waves, pathogens and drying soils. Mangrove forests, needing freshwater to survive, are endangered by rising seas. Adaptations which evolved over millions of years to help trees and forests withstand temperature extremes, defoliating herbivores, bark beetles and other infestations still can’t defend against chainsaws.

Researchers in China’s Guangde County recently discovered fossils of the oldest known forest in Asia, a stand of spore-producing trees dating back over 365 million years. These primordial trees, evolving from mossy ancestors, were among the first to proliferate. Forming forests during the Devonian period, they collectively removed CO2 from the air in sufficient amounts to cool the planet and expand polar ice caps. Today, dense foliage of tropical rainforests maintains a pivotal role in stabilizing Earth’s climate. Despite just covering 6 percent of the land surface, rainforests store more than half the world’s carbon within their plant matter. But to support agribusinesses, such as beef production, rubber, and palm oil plantations, large swaths of these ecosystems are intentionally burned, turning what once defended against climate change as carbon “sinks” into man-induced carbon emitters. The result: gross primary production (GPP) ─ defined as the amount of carbon dioxide extracted from the atmosphere and converted by plant photosynthesis into energy ─ plummets. Worse still, huge amounts of carbon sequestered for centuries in the landscape suddenly release. Logging, fire and decomposing organic matter free long-stored carbon to the atmosphere as methane, accelerating and exacerbating climate change. Wholesale destruction of forests, coupled with peat bog fires and thawing permafrost (among other positive feedback loops I’ve identified in the past), could ultimately trigger irreversible climate change “tipping points.”

No other country has lost more intact forest than Russia, even in snowy boreal ecosystems above the Arctic Circle, where wildfires and infrastructure development have wreaked havoc. Not to be outdone by myopic capitalism, woody wetlands in the southeastern United States are fast becoming pine plantations to support the wood pellet industry. Eight million tons are exported annually from the region ─ once known for its old-growth/virgin forests ─ mostly to satisfy Europe’s bio-energy fuel demands. Canada’s boreal biome meanwhile contains some of the largest proportions of healthy primary forest on Earth, but only 6% is protected. Primary forest in the U.S. Southeast, extensive up to 40 years ago, has since been decimated by exploitation. By contrast, logging bans and tree-planting efforts in China have resulted in the world’s most extensive reforestation initiative, increasing the country’s forested areas by 7% since 1990. South Korea and Vietnam have made similar progress, and over 100 global leaders last fall committed to ending deforestation worldwide by 2030.

Because big lawns and lawn care products are successfully foisted on America each year, environmental impacts of turf-grass monocultures are generally not discussed. Grasses, after all, are plants and take carbon out of the atmosphere via photosynthesis just as oak trees do. However, research strongly suggests the maintenance of turf grass lawns (i.e. mowing, watering and applying synthetic, petroleum-based fertilizers) emits considerably more greenhouse gases than they sequester. Evidence strongly suggests that tree canopy cover and naturally-kept areas with little maintenance are significantly better carbon sinks than lawns. One study in Miami-Dade County, Florida found a 4-hectare green space with 85% of its land covered in well-maintained lawn could emit over 11 tons of carbon dioxide per year, far from trivial.

Considering natural green spaces, with little to no maintenance, sequester CO2, conserve biodiversity, reduce storm water runoff, preclude fertilizer use and save the average American time, money and effort, planting trees and/or allowing wooded areas to encroach on existing lawns makes sense. “Liberty gardens” are great inflation-fighters, and prudent, ethical avoidance of palm oil, wood pellets, beef and other products derived from slash-and-burn agricultural practices around the world helps negate forest-killing consumerism. As the planet warms, municipalities need to be conscious of whether tree canopies decrease and temperatures rise while walking from wealthier neighborhoods to poorer ones. If the answer is “yes” and lack of public investment means fewer trees in low-income, largely minority areas, get out the shovels and saplings, and plant. Temperatures climb highest among sparsely-treed avenues and lots. Wooded neighborhood parks not only beat the heat and fight climate change but also provide habitat and flyways for birds while beautifying abandoned tracts of land.

I like to think of trees, especially conifers, as the plant equivalent of dinosaurs. Ponderosa pines, Douglas firs, giant sequoias and 5,000-year old bristlecones (perhaps the longest-lived individual organisms on Earth) are the true stewards and guardians of this paper-thin bubble of atmosphere supporting all life. Their grandeur, alone and united as forests, humbles us as a species, putting our insignificant foibles and enormities of our trespasses in stark and truthful perspective. We must save them in the hope of saving ourselves.

Scott Deshefy is a biologist, ecologist and two-time Green Party congressional candidate.