Forests take up carbon dioxide from the atmosphere. At the same time, forests promote the turbulent mixing of air near the surface and transpire large amounts of moisture to the atmosphere. A new study exposes the importance of these processes in keeping much of the planet’s surface cool….
Ryan M. Bright, Edouard Davin, Thomas O’Halloran, Julia Pongratz, Kaiguang Zhao, Alessandro Cescatti. Local temperature response to land cover and management change driven by non-radiative processes. Nature Climate Change, 2017; DOI: 10.1038/nclimate3250
Scientists expect trees will advance upslope as global temperatures increase, shifting the tree line—the mountain zone where trees become smaller and eventually stop growing—to higher elevations. Subalpine forests will follow their climate up the mountain, in other words. But new research suggests this may not hold true for two subalpine tree species of western North America….
…Counter to expectations, they found that warming reduced seedling survival for both species at all three elevations during the first year of life. The scientists expected survival rates to dip at the lower elevation site, where temperatures rose above the trees’ normal climate, but not higher up, where warming was expected to help seedlings. They attribute this lower survival rate to drier conditions caused by warming, which negatively affected seedling survival….
“Overall, our findings indicate that seedlings are highly vulnerable to climate variation, which should be taken into account as we predict what will happen to subalpine forests in a warming climate,” says Kueppers.
Jeff Mitton et al. Warming and provenance limit tree recruitment across and beyond the elevation range of subalpine forest. Global Change Biology, December 2016 DOI: 10.1111/gcb.13561
The state of California, wracked by drought, has 66 million dead trees across its landscape. They’ve been killed by both the drought itself and by voracious bark beetles, and now they’re just sitting there — destined to either decompose, burn in a wildfire, or be incinerated, for safety reasons, by state fire managers before the next blaze comes along.
And it isn’t just California. Raging bark beetle infestations, fanned by warmer temperatures and droughts, have also struck forests in Colorado, Wyoming, Montana, and Idaho in recent years. “About 100,000 beetle-kill trees fall every day in Wyoming and northern Colorado, to give you an idea of the order of magnitude,” says Erica Belmont, a professor of mechanical engineering at the University of Wyoming.
Belmont is studying an intriguing solution for what to do with all these dangerous dead trees — namely, burn them for energy. In a recent study in Energy Policy, Belmont and colleague Emily Beagle do the math on whether it would make sense to use the timber in existing coal plants, which can be “co-fired” with wood. In isolation, it probably costs coal plants too much money to go around rounding up dead trees, carting them back, and then burning them — a big endeavor, Belmont explained. But there are sources of possible funds. For instance, the U.S. Forest Service is currently spending considerable money to treat forests and rid them of these dangerous trees — money that, maybe, could be given to the companies that burn them for energy instead, the study suggests.
Moreover, coal plants are facing strong climate regulations, in the form of the pending Clean Power Plan. In this regulatory context, burning trees that are already destined to decompose, catch fire, or be incinerated — and thus, give off greenhouse gases to the atmosphere no matter what — could conceivably supplant some of coal’s voluminous emissions.
… Large numbers of scientists have loudly protested recent legislative attempts to decree that biomass burning is “carbon neutral” based on the logic that, even though it gives off greenhouse gas emissions just as coal does (releasing the carbon that had been stored in the tree as it grew), future tree regrowth will one day sequester those emissions once again. A leading critique of this assertion is that it takes a long time for a tree to grow back, meaning that the biomass burning is still adding carbon dioxide to the atmosphere for, at least, decades — a time period that can make a real difference for the climate and for climate policy. Moreover, there is not necessarily any guarantee that for every tree chopped down to provide electricity, another corresponding tree will regrow someday. Changing decisions about land use, for instance, could upset that assumption ….
…”The commonly-made claim that burning wood for energy is ‘carbon neutral’ is at best an exaggeration and at worst completely wrong,” said Phil Duffy, president of the Woods Hole Research Center and a prominent critic of biomass energy, after reviewing the study for the Post. “Because beetle-kill wood will decompose anyway, however, this case comes closer to being carbon neutral than others.”
But Duffy also added by email that the research may have missed some key points that complicate the analysis, such as the amount of carbon that would be required to transport dead trees to coal plants before they are even burned. He also pointed out by email that “it is not clear if they accounted for the greater emissions from wood versus coal per unit of energy produced.” Ultimately, Duffy suggested, the research might be “pretty overoptimistic about the amount of emissions saved compared to the baseline scenario (letting the wood decompose and burning pure coal).”…
Humans utilise forests and watercourses in a way that depletes ecosystem habitats, biodiversity and ecosystem services. Many areas are restored to break the trend, but to succeed you need to consider not only the ecosystem in mind, but also surrounding ecosystems. ….”Despite evident correlations between land and water ecosystems, forests and watercourses are nearly always restored separately in small-scale projects. When a forest ecosystem abounding in water has been depleted, it
can be a struggle to retain its original status by restoring only one part of it. Instead, both land and aquatic environments need to be integrated in the restoration,” says Christer Nilsson, Professor at the Department of Ecology and Environmental Sciences at Umeå University.
Riparian zones along forest rivers are environments where forests and water meet and benefit from each other. The line of trees along the riparian zones provides shade and wood. Leaves and insects falling into the water are favourable for aquatic insects and bugs and eventually also for fish. Floodings wash up sediment, seeds and other plant parts onto riparian forest zones. New plants grow, which increases production and diversity. Aquatic larvae make up a good food source for insects, spiders, crustaceans, lizards and birds on land. Decaying fish carcasses removed from the river by large animals encourage the growth of riparian trees by enriching riparian areas with nitrogen. That in turn helps trees to grow and to shed more branches and leaves into the water….Free-flowing rivers surrounded by natural forest are expected to be more resistant to climate change than streams surrounded by clearcuts or urbanised areas.
Another problem is that most studies are conducted at a local level with focus on short-term effects. Long-term recovery is often unknown and in the few cases where restorations of watercourses and forests have been coordinated, they have rarely been evaluated. Both well thought-out, basic measurements and reference areas are needed for comparisons. Good knowledge on ecosystems and their functions in the landscape are necessary to evaluate and improve the measures taken in a restoration project.
“There are complex correlations over large areas to take into account, which means that seeing the final results of small-scale projects take time. Large-scale restoration projects with a landscape perspective stand a much higher chance of succeeding. Researchers and practicians who undertake restorations are faced with immense challenges ahead,” says Christer Nilsson.
…. Of all the components of the recent Paris accord on climate change, the one that probably got the least attention but could have the most immediate potential involves the world’s forests. ….
In a section some hailed as historic, the document endorsed a United Nations mechanism for wealthier nations to pay developing countries like Brazil for reducing deforestation. …After years of progress, deforestation rates have increased recently in Brazil, and deforestation continues apace across much of the global tropics. The economic forces of agriculture and trade remain too strong to resist.
Calls for saving rainforests have a long history, but including forests as a core part of the global climate solution is “very very recent,” said Naoko Ishii, CEO of the Global Environment Facility, an international body that invests in restoring tropical forests. “Without taking care of the forests, it’s going to be just impossible to achieve the Paris agreement.”…. In fact, recent estimates suggest as much as a third of climate emissions could be offset by stopping deforestation and restoring forest land — and that this solution could be achieved much faster than cuts to fossil fuels.
Forests are a crucial “carbon sink,” living engines for absorbing and storing carbon. Tropical forests store the most carbon of all, and no tropical forest on Earth is bigger than the Amazon. It accounts for about half of all the carbon these forests store. But the Brazilian Amazon has lost nearly a fifth of its forest cover already — and the forest left behind also suffers because it is more fragmented and less continuous….
Net greenhouse gas emissions due to tropical deforestation and forest degradation are about 8 to 15 percent of the global total, which doesn’t sound like that much. But a recent study in Nature Climate Change found that stopping deforestation could nonetheless be a huge piece of the climate solution. That’s because if tropical deforestation stopped, not only would those emissions go away, but on top of that, forests would start stowing away a significant part of the carbon from our fossil fuel emissions.
“One could reduce total CO2 emissions by about 30 percent, just working in the land sector,” said Phil Duffy, president of the Woods Hole Research Center. “And that’s a lot.”.. Moreover, stopping deforestation could buy precious time to ratchet down fossil fuel emissions….