Oldspeak: “Seems reality is beginning to trickle into mainstream media indeed. Kinna hard to ignore at this point I suppose. Earth’s lungs are currently dealing with threats on multiple fronts. With recent reports of the wettest rainforest in the U.S. going up in flames, insect and pathogenic outbreaks leading to forest defoliation in the summer, and humans chopping them down at ever faster and increasingly unsustainable rates, Earth on track to lose subcontinent sized tracts of tress, the trouble for forests is getting more serious by the day. Understanding that the “biggest terrestrial sink of carbon is tied up in forests“, this is not a good sign. Just walking around Prospect Park and the streets of Brooklyn, I’ve noticed quite a few dead leaves on the ground in the middle of summer. Trees with no leaves when they’re supposed to be full of them. So this is happening everywhere there are trees, not just in forests. Something is definitely amiss.” -OSJ
Written By Chris Mooney @ The Washington Post:
“These papers document how humans have fundamentally altered forests across the globe and warn of potential broad-scale future declines in forest health, given increased demand for land and forest products combined with rapid climate change,” note Susan Trumbore of the Max Planck Institute for Biogeochemistry and two coauthors in an overarching introduction to the suite of studies.
The Science papers take the forests of the world one by one — tropical, temperate, boreal (northern), and one we don’t often think of: planted forests, sown by humans for their own use. It turns out that all four types are facing major threats, albeit in different ways:
Tropical Forests. Forests of the tropics are, in some ways, faring the worst. These crucial forests, which serve over a billion of the world’s people and provide a home for more than half of the planet’s species, are being severely impacted by logging, the transformation of forests into farmland, resource extraction, and more. “Across the world’s extant tropical forests a recent estimate suggests, 24% are intact, 46% fragmented, and 30% otherwise degraded,” write the University College London’s Simon Lewis and two colleagues in the Science paper focused on these forests.
In fact, a staggering 100 million hectares of tropical forest — roughly 386,000 square miles — were turned into farmland from 1980 to 2012, according to Lewis and colleagues. That’s an area bigger than the size of Texas — indeed, roughly half the size of Alaska.
The consequences of this change range from losing more carbon to the atmosphere and thereby worsening global warming — growing forests pull carbon in, but their loss releases it again — to killing off large numbers of species. What’s more, all of this also compounds the risk of gigantic fires. These don’t typically occur in thriving, wet tropical forests, explain Lewis and his colleagues — but they do occur if those forests are chopped up, dried out, and filled with people, who tend to start blazes accidentally.
Tropical forests aren’t unique in the problems they face. The other forest systems are in similar straits, although the details naturally vary a great deal.
Temperate Forests. Also struggling are temperate forests, such as those found in much of the lower 48 United States. For these forests, a changing climate is bringing about a particular kind of threat multiplier — droughts.
The Science study on temperate forests, by the U.S. Forest Service’s Constance Millar and the U.S. Geological Survey’s Nathan Stephenson, explains that many are now facing the threat of a new kind of intense drought — which then sets the stage for not only more burning, but also more sweeping insect and pathogen attacks. Drought also stresses and sometimes kills trees directly by reducing the amount of water that they can draw from the land through their root systems.
“In recent decades, outbreaks of insects and pathogens have resulted in millions of hectares of forest defoliation, canopy dieback, declines in growth, and forest mortality in western North America and Europe,” the authors note. “In many cases, climate was a direct or indirect trigger for these other agents of megadisturbance or influenced the severity and extent of outbreaks.”
And then, of course, there are fires — more specifically, megafires. It’s not just that they can burn up hundreds of thousands of acres of trees — it’s also a question of what grows back afterwards, and whether it provides the same services as the prior forest did, whether to humans, animal species, or the climate. “To the extent that these large fires increase in the future, the potential for shifts to new forest types and nonforest vegetation will accelerate,” Millar and Stephenson write.
Boreal forests. Perhaps the hardiest are the globe’s boreal forests, comprising 30 percent of forests overall and concentrated in the United States (Alaska), Canada, and most of all Russia. These are remote and unique regions where conditions are freezing for much of the year, and where the ground beneath is often permanently frozen (thus, featuring “permafrost”).
Few people live in these remote forests — they contain gigantic tracts of simply untouched forest land, some of the best preserved on the globe. But they’re still struggling — because of all forests on Earth, global warming is happening the fastest in this region.
Average temperature increases across many boreal forests are already 1.5 degrees Celsius, write the Canadian Forest Service’s Sylvie Gauthier and colleagues in the Science paper on these forests. And much more warming — and drying — is projected going forward, meaning that “disturbances are generally predicted to increase in extent, frequency, or severity over the same time frame, although uncertainties in the projections remain.” When forest scientists say “disturbances” they mean not only fires, but also factors like pest outbreaks.
What’s more, there’s a double whammy because these forests grow atop permafrost, which can also thaw and release carbon — a process that large wildfires can accelerate. “In Russia alone, the release of C from the thawing permafrost by the end of the century could potentially be several times larger than that of current tropical deforestation,” write Gauthier and colleagues.
“The health of the immense and seemingly timeless boreal forest is presently under threat,” they conclude.
Planted forests. And then come the world’s planted forests – also often known as “tree farms” or plantation. These make up a surprising seven percent of the world’s total forests, and could comprise much more than that by the end of the century.
Planted forests tend to be of the same type of tree species, and are managed for their resources. And what’s more, note a team of researchers from South Africa and New Zealand led by Mike Wingfield of the University of Pretoria in their Science paper, they are often comprised of trees of a species type, like Eucalyptus, that is not native to the area in which they are planted.
This sets up a really big problem, note the authors:
Non-native trees in plantations are in part successful because they have been separated from their natural enemies. However, when plantation trees are reunited with their coevolved pests, which may be introduced accidentally, or when they encounter novel pests to which they have no resistance, substantial damage or loss can ensue. The longer these non-native trees are planted in an area, the more threatened they become by native pests.
Unless major action is taken on this front, the authors continue, “pest problems will continue to grow and will threaten the long-term sustainability of forests and forestry worldwide.”
Put it all together, and it’s hard to read through the Science papers and not fear for the forests of the globe. “Many of the trees alive today will experience temperatures and CO2 levels outside the range to which they are adapted,” note Trumbore and her colleagues.
To be sure, they observe, trees will always be with us, but perhaps in a form or distribution that is, overall, quite changed. And not only are we causing all of this — in the end, it would hurt us most of all.
“Human concerns about forest health mostly reflect our dependence on the continued availability of the products and services that forests provide,” the authors conclude.
Earth is on track to lose an India-sized chunk of its tropical forests by mid-century
Written By Chelsea Harvey @ The Washington Post:
There are some limitations to the data set the researchers used. For one thing, the satellite data are unable to distinguish between different types of tree cover, meaning tree plantations get lumped in with natural forests. This means there’s the potential for the data set to over- or underestimate the amount of natural forest being lost each year, and the researchers say future studies should attempt to investigate this issue. However, the data otherwise turned up some alarming findings.
“Unlike many previous studies, we actually project that if we do nothing, deforestation in the tropics will accelerate,” says Jonah Busch, one of the authors and a research fellow at the Center for Global Development. (Busch published the study along with colleague Jens Engelmann.) Judging from the patterns they observed using the satellite data, the researchers believe that deforestation under a business-as-usual scenario will climb steadily for the next several decades and then slightly accelerate in the 2040s.
Losing so much of the world’s forests is bad enough for the plants and animals that depend on them to survive. But even more alarming are the implications for global climate change. Currently, world leaders are working to keep global temperatures from rising more than 2 degrees Celsius. But in order to meet that goal, scientists say, there’s a limited amount of carbon humans can continue to pour into the atmosphere in the coming decades.
Cutting down on the burning of fossil fuels and transitioning to renewable energy sources is a major way nations around the world are working to meet the 2-degree goal. But forests contain huge stores of carbon as well, which get dumped into the atmosphere if the trees are destroyed. The new paper points out that the India-sized chunk of tropical forest we’ll lose under a business-as-usual trajectory will release about 169 gigatons of carbon dioxide into the atmosphere — that’s a sixth of our remaining carbon budget. These emissions are tantamount to what would happen if we ran approximately 44,000 new coal plants per year, Busch says.
That’s a substantial portion of the budget to burn through by mid-century. But the researchers say there are several effective ways to start cutting down on deforestation. Setting up international carbon payments — in which wealthy countries pay other nations to keep their tropical forests standing — is one option. Introducing domestic carbon prices, which are essentially taxes that must be paid for the right to emit a certain amount of carbon, is another possibility. Or countries could simply enact more restrictive policies on deforestation. In fact, some nations have already enacted such policies or have pledged to enact them in the future, offering hope that the dire scenario described in the paper could still be avoided.
The researchers checked out how much carbon could be saved by introducing these policies all over the world. They found that universally applying a price of $20 per ton of carbon dioxide between 2016 and 2050 would prevent 41 gigatons of carbon dioxide from being emitted due to forest destruction. And a price of $50 per ton would save 77 gigatons of carbon dioxide.
Simple anti-deforestation policies can be effective too. The researchers used the policies enacted in Brazil as a model since, as Busch says, “Brazil has been the world’s biggest climate success story in the last decade.” Since 2004, he says, the country has slashed deforestation of the Amazon by nearly 80 percent. The researchers found that if all countries enacted anti-deforestation policies as effective as those in Brazil, 60 gigatons of carbon emissions could be avoided.
One other important point to note, according to Busch, is that reducing emissions from deforestation is relatively cheap compared to reducing emissions from other sectors, such as energy or transportation. Emissions from tropical deforestation are about equivalent to emissions put out by the European Union, Busch says — but cutting down on deforestation through any of the means described above only costs about a fifth of what it would take to cut an equivalent amount of emissions in the European Union.
It’s an opportunity for the world to address a significant carbon source in a comparatively cheap way, the authors argue. And, according to Busch, it’s also an opportunity for wealthy countries such as the United States to step up and start putting more money into international carbon payments or other global deforestation efforts.
“This is a real opportunity for the U.S. to show leadership, and not just leadership at home, but internationally,” Busch says. “[U.S.] funding in this area is quite small at the moment, so a little more could go a long way.”