Earth Overshoot Day marks the date when humanity’s demand for ecological resources and services in a given year exceeds what Earth can regenerate in that year.
The day was pushed back this year slightly as the pandemic slowed runaway overconsumption. That’s a good thing! Let’s move the date further!
August 20, 2020 by Tim Radford, Climate News Network (CC BY-ND 4.0)
LONDON, 20 August, 2020 – There is one straightforward way to reduce greenhouse gases: by taking better care of the world’s natural forests.
European and US scientists think they may have settled a complex argument about how to restore a natural forest so that it absorbs more carbon. Don’t just leave nature to regenerate in the way she knows best. Get into the woodland and manage, and plant.
It will cost more money, but it will sequester more carbon: potentially enough to make economic good sense.
Researchers from 13 universities and research institutions report in the journal Science that they carefully mapped and then studied a stretch of tropical forest in Sabah, in Malaysian Borneo: a forest that had been heavily logged more than 30 years ago, and converted to plantation, and then finally protected from further damage. The mapping techniques recorded where, and how much, above-ground carbon was concentrated, across thousands of hectares.
The researchers report that those reaches of forest left to regenerate without human help recovered by as much as 2.9 tonnes of above-ground carbon per hectare each year. But those areas of forest that were helped a little, by what the scientists call “active restoration”, did even better.
Humans entered the regenerating forests and cut back the lianas – the climbing plants that flourish in degraded forests and compete with saplings – to help seedlings flourish. They also weeded where appropriate and enriched the mix of new plants with native seedlings.
Where this happened, the forest recovered 50% faster and carbon storage above-ground per hectare was measured at between 2.9 tonnes per hectare and 4.4 tonnes.
The lesson to be drawn is that where a natural forest may be thought fully restored after 60 years, active restoration could make it happen in 40 years.
Restoration helps previously over-used forests not only to recover carbon, but also to become ecologically sound and diverse again”
—Christopher Philipson, Swiss Federal Technology Institute
The research demonstrates two things. The first is that forests can and will restore themselves: opportunistic plants will colonise open space and provide cover for those species best adapted to long-term survival in that climate and habitat. Nature will decide what conservationists call “the climax vegetation” of any natural forest. The second is that nature can indeed benefit from selective human help.
“This active restoration encourages naturally diverse forest, and is therefore much more beneficial for biodiversity than monocultures or plantation forests,” said Christopher Philipson, of the Swiss Federal Technology Institute known as ETH Zurich.
“In this way restoration helps previously over-used forests not only to recover carbon, but also to become ecologically sound and diverse again.”
There will be arguments about the finding. One is that what might be a good solution in south-east Asia might not be the best answer for the Congo or parts of the Amazon: as humans degrade the forest, they may also affect the local climate in ways that favour some native species rather than others. That is, it might never be possible to restore a forest to what it had been before the forester’s axe arrived.
There is a second argument: restoration work costs money. How much economic sense it makes depends on what value scientists, politicians and economists put on the carbon that is sequestered as a consequence, and what price humanity pays for that same carbon in the form of additional greenhouse gas that will raise global temperatures, alter rainfall patterns and trigger potentially catastrophic climate change.
What worth do forests have to local populations, and what is the value set on the world’s wildernesses as global natural capital?
“Not long ago we treated degraded tropical forests as lost causes,” said a co-author, Greg Asner of Arizona State University.
“Our new findings, combined with those of other researchers around the world, strongly suggest that restoring tropical forests is a viable and highly scalable solution to regaining lost carbon stocks on land.” – Climate News Network
By Gustaf Hugelius, Senior Lecturer, Physical Geography, Stockholm University, World Economic Forum published in collaboration with The Conversation (Public License).
Peatlands cover just a few percent of the global land area but they store almost one-quarter of all soil carbon and so play a crucial role in regulating the climate. My colleagues and I have just produced the most accurate map yet of the world’s peatlands – their depth, and how much greenhouse gas they have stored. We found that global warming will soon mean that these peatlands start emitting more carbon than they store.
Peatlands form in areas where waterlogged conditions slow down the decomposition of plant material and peat accumulates. This accumulation of carbon-rich plant remains has been especially strong in northern tundra and taiga areas where they have helped cool the global climate for more than 10,000 years. Now, large areas of perennially frozen (permafrost) peatlands are thawing, causing them to rapidly release the freeze-locked carbon back into the atmosphere as carbon dioxide and methane.
Geoscientists have studied peatlands for a long time. They’ve looked at why some areas have peat but others don’t and they’ve looked at how peatlands work as natural archives through which we can reconstruct what the climate and vegetation was like in the past (or even what human life was life: many well-preserved ancient humans have been found in peat bogs).
Scientists have also long recognised that peatlands are important parts of the global carbon cycle and the climate. When plants grow they absorb CO₂ from the atmosphere and as this material accumulates in the peat, there is less carbon in the atmosphere and therefore the climate will cool in the long-term.
With all this knowledge about how important northern peatlands are, it is perhaps surprising to learn that, until recently, there was no comprehensive map of their depth and how much carbon they store. That is why I led an international group of researchers who put together such a map, which we can use to estimate how the peatlands will respond to global warming. Our work is now published in the journal PNAS.
Peatlands are surprisingly difficult to map as their growth is connected to many different local factors, such as how water drains in the landscape. This meant we had to gather more than 7,000 field observations and use new statistical models based on machine learning to create the maps.
We found that peatlands cover approximately 3.7 million square kilometres. If it were a country, “Peatland” would be slightly larger than India. These peatlands also store approximately 415 gigatons (billion tons) of carbon – as much as is stored in all the world’s forests and trees together.
Almost half of this northern peatland carbon is presently in permafrost, ground that is frozen all year round. But, as the world warms and permafrost thaws, it causes peatlands to collapse and completely changes how they relate to greenhouse gases. Areas that once cooled the atmosphere by storing carbon would instead release more of both CO₂ and methane than they stored. We found that the thaw projected from future global warming will cause releases of greenhouse gas that overshadow and reverse the carbon dioxide sink of all northern peatlands for several hundred years. The exact timing of this switch is still highly uncertain, but it is likely to happen in the later half of this century.
There are regions of very extensive permafrost peatlands in Western Siberia and around Hudson Bay in Canada. These unique environments and ecosystems will be fundamentally changed as the permafrost thaws, and their characteristic mix of frozen peat mounds and small lakes will be replaced by extensive areas of wet fens.
These changes will cause more CO₂ and methane to be released into the atmosphere as the previously frozen peat becomes available for microbes that degrade it. The thaw will also lead to large losses of peat into rivers and streams, which will influence both the food chains and biochemistry of inland waters and the Arctic Ocean.
These new finding further reinforce how urgent it is to rapidly reduce our emissions, as the only way to stop permafrost thaw is to limit global warming. There are no geoengineering solutions that can be deployed in these vast and remote areas. Our results clearly show that more limited global warming of 1.5℃-2℃ would be much less damaging than our current trajectories of 3℃-4℃ degrees or above.