One morning in 2009, I sat on a creaky bus winding its way up a mountainside in central Costa Rica, light-headed from diesel fumes as I clutched my many suitcases. They contained thousands of test tubes and sample vials, a toothbrush, a waterproof notebook and two changes of clothes.
I was on my way to La Selva Biological Station, where I was to spend several months studying the wet, lowland rainforest’s response to increasingly common droughts. On either side of the narrow highway, trees bled into the mist like watercolours into paper, giving the impression of an infinite primeval forest bathed in cloud.
As I gazed out of the window at the imposing scenery, I wondered how I could ever hope to understand a landscape so complex. I knew that thousands of researchers across the world were grappling with the same questions, trying to understand the fate of tropical forests in a rapidly changing world.
Our society asks so much of these fragile ecosystems, which control freshwater availability for millions of people and are home to two thirds of the planet’s terrestrial biodiversity. And increasingly, we have placed a new demand on these forests – to save us from human-caused climate change.
Plants absorb CO₂ from the atmosphere, transforming it into leaves, wood and roots. This everyday miracle has spurred hopes that plants – particularly fast growing tropical trees – can act as a natural brake on climate change, capturing much of the CO₂ emitted by fossil fuel burning. Across the world, governments, companies and conservation charities have pledged to conserve or plant massive numbers of trees.
But the fact is that there aren’t enough trees to offset society’s carbon emissions – and there never will be. I recently conducted a review of the available scientific literature to assess how much carbon forests could feasibly absorb. If we absolutely maximised the amount of vegetation all land on Earth could hold, we’d sequester enough carbon to offset about ten years of greenhouse gas emissions at current rates. After that, there could be no further increase in carbon capture.
Yet the fate of our species is inextricably linked to the survival of forests and the biodiversity they contain. By rushing to plant millions of trees for carbon capture, could we be inadvertently damaging the very forest properties that make them so vital to our wellbeing? To answer this question, we need to consider not only how plants absorb CO₂, but also how they provide the sturdy green foundations for ecosystems on land.
How plants fight climate change
Plants convert CO₂ gas into simple sugars in a process known as photosynthesis. These sugars are then used to build the plants’ living bodies. If the captured carbon ends up in wood, it can be locked away from the atmosphere for many decades. As plants die, their tissues undergo decay and are incorporated into the soil.
While this process naturally releases CO₂ through the respiration (or breathing) of microbes that break down dead organisms, some fraction of plant carbon can remain underground for decades or even centuries. Together, land plants and soils hold about 2,500 gigatonnes of carbon – about three times more than is held in the atmosphere.
Because plants (especially trees) are such excellent natural storehouses for carbon, it makes sense that increasing the abundance of plants across the world could draw down atmospheric CO₂ concentrations.
Plants need four basic ingredients to grow: light, CO₂, water and nutrients (like nitrogen and phosphorus, the same elements present in plant fertiliser). Thousands of scientists across the world study how plant growth varies in relation to these four ingredients, in order to predict how vegetation will respond to climate change.
This is a surprisingly challenging task, given that humans are simultaneously modifying so many aspects of the natural environment by heating the globe, altering rainfall patterns, chopping large tracts of forest into tiny fragments and introducing alien species where they don’t belong. There are also over 350,000 species of flowering plants on land and each one responds to environmental challenges in unique ways.
Due to the complicated ways in which humans are altering the planet, there is a lot of scientific debate about the precise quantity of carbon that plants can absorb from the atmosphere. But researchers are in unanimous agreement that land ecosystems have a finite capacity to take up carbon.
If we ensure trees have enough water to drink, forests will grow tall and lush, creating shady canopies that starve smaller trees of light. If we increase the concentration of CO₂ in the air, plants will eagerly absorb it – until they can no longer extract enough fertiliser from the soil to meet their needs. Just like a baker making a cake, plants require CO₂, nitrogen and phosphorus in particular ratios, following a specific recipe for life.
In recognition of these fundamental constraints, scientists estimate that the earth’s land ecosystems can hold enough additional vegetation to absorb between 40 and 100 gigatonnes of carbon from the atmosphere. Once this additional growth is achieved (a process which will take a number of decades), there is no capacity for additional carbon storage on land.
But our society is currently pouring CO₂ into the atmosphere at a rate of ten gigatonnes of carbon a year. Natural processes will struggle to keep pace with the deluge of greenhouse gases generated by the global economy. For example, I calculated that a single passenger on a round trip flight from Melbourne to New York City will emit roughly twice as much carbon (1600 kg C) as is contained in an oak tree half a meter in diameter (750 kg C).
Peril and promise
Despite all these well recognised physical constraints on plant growth, there is a proliferating number of large scale efforts to increase vegetation cover to mitigate the climate emergency – a so called “nature-based” climate solution. The vastmajority of these efforts focus on protecting or expanding forests, as trees contain many times more biomass than shrubs or grasses and therefore represent greater carbon capture potential.
Yet fundamental misunderstandings about carbon capture by land ecosystems can have devastating consequences, resulting in losses of biodiversity and an increase in CO₂ concentrations. This seems like a paradox – how can planting trees negatively impact the environment?
The answer lies in the subtle complexities of carbon capture in natural ecosystems. To avoid environmental damage, we must refrain from establishing forests where they naturally don’t belong, avoid “perverse incentives” to cut down existing forest in order to plant new trees, and consider how seedlings planted today might fare over the next several decades.
Before undertaking any expansion of forest habitat, we must ensure that trees are planted in the right place because not all ecosystems on land can or should support trees. Planting trees in ecosystems that are normally dominated by other types of vegetation often fails to result in long term carbon sequestration.
One particularly illustrative example comes from Scottish peatlands – vast swathes of land where the low-lying vegetation (mostly mosses and grasses) grows in constantly soggy, moist ground. Because decomposition is very slow in the acidic and waterlogged soils, dead plants accumulate over very long periods of time, creating peat. It’s not just the vegetation that is preserved: peat bogs also mummify so-called “bog bodies” – the nearly intact remains of men and women who died millennia ago. In fact, UK peatlands contain 20 times more carbon than found in the nation’s forests.
But in the late 20th century, some Scottish bogs were drained for tree planting. Drying the soils allowed tree seedlings to establish, but also caused the decay of the peat to speed up. Ecologist Nina Friggens and her colleagues at the University of Exeter estimated that the decomposition of drying peat released more carbon than the growing trees could absorb. Clearly, peatlands can best safeguard the climate when they are left to their own devices.
The same is true of grasslands and savannahs, where fires are a natural part of the landscape and often burn trees that are planted where they don’t belong. This principle also applies to Arctic tundras, where the native vegetation is covered by snow throughout the winter, reflecting light and heat back to space. Planting tall, dark-leaved trees in these areas can increase absorption of heat energy, and lead to local warming.
But even planting trees in forest habitats can lead to negative environmental outcomes. From the perspective of both carbon sequestration and biodiversity, all forests are not equal – naturally established forests contain more species of plants and animals than plantation forests. They often hold more carbon, too. But policies aimed at promoting tree planting can unintentionally incentivise deforestation of well established natural habitats.
A recent high-profile example concerns the Mexican government’s Sembrando Vida programme, which provides direct payments to landowners for planting trees. The problem? Many rural landowners cut down well established older forest to plant seedlings. This decision, while quite sensible from an economic point of view, has resulted in the loss of tens of thousands of hectares of mature forest.
This example demonstrates the risks of a narrow focus on trees as carbon absorption machines. Many well meaning organisations seek to plant the trees which grow the fastest, as this theoretically means a higher rate of CO₂ “drawdown” from the atmosphere.
Yet from a climate perspective, what matters is not how quickly a tree can grow, but how much carbon it contains at maturity, and how long that carbon resides in the ecosystem. As a forest ages, it reaches what ecologists call a “steady state” – this is when the amount of carbon absorbed by the trees each year is perfectly balanced by the CO₂ released through the breathing of the plants themselves and the trillions of decomposer microbes underground.
This phenomenon has led to an erroneous perception that old forests are not useful for climate mitigation because they are no longer growing rapidly and sequestering additional CO₂. The misguided “solution” to the issue is to prioritise tree planting ahead of the conservation of already established forests. This is analogous to draining a bathtub so that the tap can be turned on full blast: the flow of water from the tap is greater than it was before – but the total capacity of the bath hasn’t changed. Mature forests are like bathtubs full of carbon. They are making an important contribution to the large, but finite, quantity of carbon that can be locked away on land, and there is little to be gained by disturbing them.
What about situations where fast growing forests are cut down every few decades and replanted, with the extracted wood used for other climate-fighting purposes? While harvested wood can be a very good carbon store if it ends up in long lived products (like houses or other buildings), surprisingly little timber is used in this way.
Similarly, burning wood as a source of biofuel may have a positive climate impact if this reduces total consumption of fossil fuels. But forests managed as biofuel plantations provide little in the way of protection for biodiversity and some research questions the benefits of biofuels for the climate in the first place.
Fertilise a whole forest
Scientific estimates of carbon capture in land ecosystems depend on how those systems respond to the mounting challenges they will face in the coming decades. All forests on Earth – even the most pristine – are vulnerable to warming, changes in rainfall, increasingly severe wildfires and pollutants that drift through the Earth’s atmospheric currents.
Some of these pollutants, however, contain lots of nitrogen (plant fertiliser) which could potentially give the global forest a growth boost. By producing massive quantities of agricultural chemicals and burning fossil fuels, humans have massively increased the amount of “reactive” nitrogen available for plant use. Some of this nitrogen is dissolved in rainwater and reaches the forest floor, where it can stimulate tree growth in some areas.
As a young researcher fresh out of graduate school, I wondered whether a type of under-studied ecosystem, known as seasonally dry tropical forest, might be particularly responsive to this effect. There was only one way to find out: I would need to fertilise a whole forest.
Working with my postdoctoral adviser, the ecologist Jennifer Powers, and expert botanist Daniel Pérez Avilez, I outlined an area of the forest about as big as two football fields and divided it into 16 plots, which were randomly assigned to different fertiliser treatments. For the next three years (2015-2017) the plots became among the most intensively studied forest fragments on Earth. We measured the growth of each individual tree trunk with specialised, hand-built instruments called dendrometers.
We used baskets to catch the dead leaves that fell from the trees and installed mesh bags in the ground to track the growth of roots, which were painstakingly washed free of soil and weighed. The most challenging aspect of the experiment was the application of the fertilisers themselves, which took place three times a year. Wearing raincoats and goggles to protect our skin against the caustic chemicals, we hauled back-mounted sprayers into the dense forest, ensuring the chemicals were evenly applied to the forest floor while we sweated under our rubber coats.
Unfortunately, our gear didn’t provide any protection against angry wasps, whose nests were often concealed in overhanging branches. But, our efforts were worth it. After three years, we could calculate all the leaves, wood and roots produced in each plot and assess carbon captured over the study period. We found that most trees in the forest didn’t benefit from the fertilisers – instead, growth was strongly tied to the amount of rainfall in a given year.
This suggests that nitrogen pollution won’t boost tree growth in these forests as long as droughts continue to intensify. To make the same prediction for other forest types (wetter or drier, younger or older, warmer or cooler) such studies will need to be repeated, adding to the library of knowledge developed through similar experiments over the decades. Yet researchers are in a race against time. Experiments like this are slow, painstaking, sometimes backbreaking work and humans are changing the face of the planet faster than the scientific community can respond.
Humans need healthy forests
Supporting natural ecosystems is an important tool in the arsenal of strategies we will need to combat climate change. But land ecosystems will never be able to absorb the quantity of carbon released by fossil fuel burning. Rather than be lulled into false complacency by tree planting schemes, we need to cut off emissions at their source and search for additional strategies to remove the carbon that has already accumulated in the atmosphere.
Does this mean that current campaigns to protect and expand forest are a poor idea? Emphatically not. The protection and expansion of natural habitat, particularly forests, is absolutely vital to ensure the health of our planet. Forests in temperate and tropical zones contain eight out of every ten species on land, yet they are under increasing threat. Nearly half of our planet’s habitable land is devoted to agriculture, and forest clearing for cropland or pasture is continuing apace.
Meanwhile, the atmospheric mayhem caused by climate change is intensifying wildfires, worsening droughts and systematically heating the planet, posing an escalating threat to forests and the wildlife they support. What does that mean for our species? Again and again, researchers have demonstrated strong links between biodiversity and so-called “ecosystem services” – the multitude of benefits the natural world provides to humanity.
Carbon capture is just one ecosystem service in an incalculably long list. Biodiverse ecosystems provide a dizzying array of pharmaceutically active compounds that inspire the creation of new drugs. They provide food security in ways both direct (think of the millions of people whose main source of protein is wild fish) and indirect (for example, a large fraction of crops are pollinated by wild animals).
Natural ecosystems and the millions of species that inhabit them still inspire technological developments that revolutionise human society. For example, take the polymerase chain reaction (“PCR”) that allows crime labs to catch criminals and your local pharmacy to provide a COVID test. PCR is only possible because of a special protein synthesised by a humble bacteria that lives in hot springs.
As an ecologist, I worry that a simplistic perspective on the role of forests in climate mitigation will inadvertently lead to their decline. Many tree planting efforts focus on the number of saplings planted or their initial rate of growth – both of which are poor indicators of the forest’s ultimate carbon storage capacity and even poorer metric of biodiversity. More importantly, viewing natural ecosystems as “climate solutions” gives the misleading impression that forests can function like an infinitely absorbent mop to clean up the ever increasing flood of human caused CO₂ emissions.
Luckily, many big organisations dedicated to forest expansion are incorporating ecosystem health and biodiversity into their metrics of success. A little over a year ago, I visited an enormous reforestation experiment on the Yucatán Peninsula in Mexico, operated by Plant-for-the-Planet – one of the world’s largest tree planting organisations. After realising the challenges inherent in large scale ecosystem restoration, Plant-for-the-Planet has initiated a series of experiments to understand how different interventions early in a forest’s development might improve tree survival.
But that is not all. Led by Director of Science Leland Werden, researchers at the site will study how these same practices can jump-start the recovery of native biodiversity by providing the ideal environment for seeds to germinate and grow as the forest develops. These experiments will also help land managers decide when and where planting trees benefits the ecosystem and where forest regeneration can occur naturally.
Viewing forests as reservoirs for biodiversity, rather than simply storehouses of carbon, complicates decision making and may require shifts in policy. I am all too aware of these challenges. I have spent my entire adult life studying and thinking about the carbon cycle and I too sometimes can’t see the forest for the trees. One morning several years ago, I was sitting on the rainforest floor in Costa Rica measuring CO₂ emissions from the soil – a relatively time intensive and solitary process.
As I waited for the measurement to finish, I spotted a strawberry poison dart frog – a tiny, jewel-bright animal the size of my thumb – hopping up the trunk of a nearby tree. Intrigued, I watched her progress towards a small pool of water held in the leaves of a spiky plant, in which a few tadpoles idly swam. Once the frog reached this miniature aquarium, the tiny tadpoles (her children, as it turned out) vibrated excitedly, while their mother deposited unfertilised eggs for them to eat. As I later learned, frogs of this species (Oophaga pumilio) take very diligent care of their offspring and the mother’s long journey would be repeated every day until the tadpoles developed into frogs.
It occurred to me, as I packed up my equipment to return to the lab, that thousands of such small dramas were playing out around me in parallel. Forests are so much more than just carbon stores. They are the unknowably complex green webs that bind together the fates of millions of known species, with millions more still waiting to be discovered. To survive and thrive in a future of dramatic global change, we will have to respect that tangled web and our place in it.
Carbon dioxide is being accumulated in the atmosphere at the fastest rate since records began, as scientists warn that the oceans and forests may have absorbed so much CO2 that their crucial function as “carbon sinks” is now severely threatened.
The jump in atmospheric CO2 is partly the result of rising carbon emissions as the world burns ever-more fossil fuels, according to the latest World Meteorological Organisation report, which finds the concentration of carbon increased by nearly three parts per million (ppm) to 396ppm last year.
But, crucially, preliminary data in the report indicates that the jump could also be attributed to “reduced CO2 uptake by the Earth’s biosphere” – the first time the effectiveness of the world’s great carbon sinks has been scientifically called into question.
Scientists said they were puzzled and extremely concerned by prospect of reduced absorption of the world’s oceans and plants, which they cannot explain and which threatens to accelerate the build-up of heat-trapping greenhouse gases in the atmosphere if the trend continues.
“That carbon dioxide concentrations continued to surge upwards last year is worrying news,” said Professor Dave Reay, of the University of Edinburgh.
“Of particular concern is the indication that carbon storage in the world’s forests and oceans may be faltering. So far these ‘carbon sinks’ have been locking away almost half of all the carbon dioxide we emit,” Professor Reay added.
“If they begin to fail in the face of further warming then our chances of avoiding dangerous climate change become very slim indeed.”
The plants and the oceans each typically absorb about a quarter of humanity’s CO2 emissions every year, with the other half going into the atmosphere, where it can remain for hundreds of years.
The last time there was a reduction in the biosphere’s ability to absorb carbon was in 1998, a year in which extensive forest fires and dry weather killed off lots of plants, dealing a blow to the world’s carbon sink.
But Dr Oksana Tarasova, chief of the atmospheric research division at the WMO, said this time it is much more worrying because there have been no obvious impacts on the biosphere this year.
“This problem is very serious. It could be that the biosphere is already at its limit, or it may be close to reaching it. Or it may be that it just becomes less effective at absorbing carbon. But it’s still very concerning,” said Dr Tarasova.
The worst-case scenario in which the carbon sink ceased to function at all would double the rate at which CO2 emissions accumulate in the atmosphere, significantly increasing the fallout of climate change, such as storms, droughts and temperature increases, Dr Tarasova said.
The latest WMO survey packed a second environmental punch – revealing that the oceans are currently acidifying at a rate that is unprecedented in the past 300 million years.
This is because they are absorbing about 4kg of carbon dioxide for every person on the planet, the report says.
The WMO’s findings intensified calls for co-ordinated global action to limit global warming to 2C, beyond which its consequences become increasingly devastating.
“We are running out of time. Past, present and future CO2 emissions will have a cumulative impact on both global warming and ocean acidification. The law of physics are non-negotiable,” said the WMO’s secretary-general Michel Jarraud. He added that, rather than rising, fossil fuel and other emissions badly need to come down.
In June 1988, climatologist and NASA scientist James Hansen stood before the Energy and Natural Resources Committee in the United States Senate. The temperature was a sweltering 98 degrees.
“The earth is warmer in 1988 than at any time in the history of instrumental measurements,” Hansen said. “The global warming now is large enough that we can ascribe with a high degree of confidence a cause-and-effect relationship to the greenhouse effect… Our computer climate simulations indicate that the greenhouse effect is already large enough to begin to effect the probability of extreme events such as summer heat waves.”
Hansen has authored some of the most influential scientific literature around climate change, and like the vast majority of climate scientists, has focused his work on the last 150 to 200 years – the period since the industrial revolution.
This period has been characterized by the widespread release of greenhouse gases like carbon dioxide (CO2) and methane (CH4), and by the clearing of land on a massive scale – the plowing of grasslands and felling of forests for cities and agricultural crops.
Now, the world is on the brink of catastrophic climate change. Hansen and other scientists warn us that if civilization continues to burn fossil fuels and clear landscapes, natural cycles may be disrupted to the point of complete ecosystem breakdown – a condition in which the planet is too hot to support life. Hansen calls this the Venus Syndrome, named after the boiling planet enshrouded in clouds of greenhouse gases.
“If we also burn the tar sands and tar shale [low grade, high carbon fossil fuels], I believe the Venus syndrome is a dead certainty,” Hansen has said.
If humanity wishes to have a chance of avoiding this fate, it is important that we understand global warming in detail. Why is it happening? When did it start? What fuels it? And, most importantly, what can stop it?
How old is global warming?
New studies are showing that the current episode of global warming may be a great deal older than previously believed – which may entirely change our strategy to stop it.
While fossil fuels have only been burned on a large scale for 200 years, land clearance has been a defining characteristic of civilizations – cultures based around cities and agriculture – since they first emerged around 8,000 years ago.
This land clearance has impacts on global climate. When a forest ecosystem is converted to agriculture, more than two thirds of the carbon that was stored in that forest is lost, and additional carbon stored in soils rich in organic materials will continue to be lost to the atmosphere as erosion accelerates.
Modern science may give us an idea of the magnitude of the climate impact of this pre-industrial land clearance. Over the past several decades of climate research, there has been an increasing focus on the impact of land clearance on modern global warming. The Intergovernmental Panel on Climate Change, in it’s 2004 report, attributed 17% of global emissions to cutting forests and destroying grasslands – a number which does not include the loss of future carbon storage or emissions directly related to this land clearance, such as methane released from rice paddies or fossil fuels burnt for heavy equipment.
Some studies show that 50% of the global warming in the United States can be attributed to land clearance – a number that reflects the inordinate impact that changes in land use can have on temperatures, primarily by reducing shade cover and evapotranspiration (the process whereby a good-sized tree puts out thousands of gallons of water into the atmosphere on a hot summer day – their equivalent to our sweating).
So if intensive land clearance has been going on for thousands of years, has it contributed to global warming? Is there a record of the impacts of civilization in the global climate itself?
10,000 years of Climate Change
According to author Lierre Keith, the answer is a resounding yes. Around 10,000 years ago, humans began to cultivate crops. This is the period referred to as the beginning of civilization, and, according to the Keith and other scholars such as David Montgomery, a soil scientist at the University of Washington, it marked the beginning of land clearance and soil erosion on a scale never before seen – and led to massive carbon emissions.
“In Lebanon (and then Greece, and then Italy) the story of civilization is laid bare as the rocky hills,” Keith writes. “Agriculture, hierarchy, deforestation, topsoil loss, militarism, and imperialism became an intensifying feedback loop that ended with the collapse of a bioregion [the Mediterranean basin] that will most likely not recover until after the next ice age.”
Montgomery writes, in his excellent book Dirt: The Erosion of Civilizations, that the agriculture that followed logging and land clearance led to those rocky hills noted by Keith.
“It is my contention that the invention of [agriculture] fundamentally altered the balance between soil production and soil erosion – dramatically increasing soil erosion.
Other researchers, like Jed Kaplan and his team from the Avre Group at the Ecole Polytechnique Fédérale de Lausanne in Switzerland, have affirmed that preindustrial land clearance has had a massive impact on the landscape.
“It is certain that the forests of many European countries were substantially cleared before the Industrial Revolution,” they write in a 2009 study.
Their data shows that forest cover declined from 35% to 0% in Ireland over the 2800 years before the beginning of the Industrial Revolution. The situation was similar in Norway, Finland, Iceland, where 100% of the arable land was cleared before 1850.
Similarly, the world’s grasslands have been largely destroyed: plowed under for fields of wheat and corn, or buried under spreading pavement. The grain belt, which stretches across the Great Plains of the United States and Canada, and across much of Eastern Europe, southern Russia, and northern China, has decimated the endless fields of constantly shifting native grasses.
The same process is moving inexorably towards its conclusion in the south, in the pampas of Argentina and in the Sahel in Africa. Thousands of species, each uniquely adapted to the grasslands that they call home, are being driven to extinction.
“Agriculture in any form is inherently unsustainable,” writes permaculture expert Toby Hemenway. “We can pass laws to stop some of the harm agriculture does, but these rules will reduce harvests. As soon as food gets tight, the laws will be repealed. There are no structural constraints on agriculture’s ecologically damaging tendencies.”
As Hemenway notes, the massive global population is essentially dependent on agriculture for survival, which makes political change a difficult proposition at best. The seriousness of this problem is not to be underestimated. Seven billion people are dependent on a food system – agricultural civilization – that is killing the planet.
The primary proponent of the hypothesis – that human impacts on climate are as old as civilization – has been Dr. William Ruddiman, a retired professor at the University of Virginia. The theory is often called Ruddiman’s Hypothesis, or, alternately, the Early Anthropocene Hypothesis.
Ruddiman’s research, which relies heavily on atmospheric data from gases trapped in thick ice sheets in Antarctica and Greenland, shows that around 11,000 years ago carbon dioxide levels in the atmosphere began to decline as part of a natural cycle related to the end of the last Ice Age. This reflected a natural pattern that has been seen after previous ice ages.
This decline continued until around 8000 years ago, when the natural trend of declining carbon dioxide turned around, and greenhouse gases began to rise. This coincides with the spread of civilization across more territory in China, India, North Africa, the Middle East, and certain other regions.
Ruddiman’s data shows that deforestation over the next several thousand years released 350 Gigatonnes of carbon into the atmosphere, an amount nearly equal to what has been released since the Industrial Revolution. The figure is corroborated by the research of Kaplan and his team.
Around 5000 years ago, cultures in East and Southeast Asia began to cultivate rice in paddies – irrigated fields constantly submerged in water. Like an artificial wetland, rice patties create an anaerobic environment, where bacteria metabolizing carbon-based substances (like dead plants) release methane instead of carbon dioxide and the byproduct of their consumption. Ruddiman points to a spike in atmospheric methane preserved in ice cores around 5000 years ago as further evidence of warming due to agriculture.
Some other researchers, like R. Max Holmes from the Woods Hole Research Institute and Andrew Bunn, a climate scientist from Western Washington University, believe that evidence is simply not conclusive. Data around the length of interglacial periods and the exact details of carbon dioxide and methane trends is not detailed enough to make a firm conclusion, they assert. Regardless, it is certain that the pre-industrial impact of civilized humans on the planet was substantial.
“Our data show very substantial amounts of human impact on the environment over thousands of years,” Kaplan said. “That impact really needs to be taken into account when we think about the carbon cycle and greenhouse gases.”
Restoring Grasslands: a strategy for survival
If the destruction of grasslands and forests signals the beginning of the end for the planet’s climate, some believe that the restoration of these natural communities could mean salvation.
Beyond their beauty and inherent worth, intact grasslands supply a great deal to humankind. Many pastoral cultures subsist entirely on the animal protein that is so abundant in healthy grasslands. In North America, the rangelands that once sustained more than 60 million Bison (and at least as many pronghorn antelope, along with large populations of elk, bear, deer, and many others) now support fewer than 45 million cattle – animals ill-adapted to the ecosystem, who damage their surroundings instead of contributing to them.
Healthy populations of herbivores also contribute to carbon sequestration in grassland soils by increasing nutrient recycling, a powerful effect that allows these natural communities to regulate world climate. They also encourage root growth, which sequesters more carbon in the soil.
Just as herbivores cannot survive without grass, grass cannot thrive without herbivores.
Grasslands are so potent in their ability to pull carbon dioxide out of the atmosphere that some believe restoring natural grasslands could be one of the most effective tools in the fight against runaway global warming.
“Grass is so good at building [carbon rich] soil that repairing 75 percent of the planet’s rangelands would bring atmospheric CO2 to under 330 ppm in 15 years or less,” Lierre Keith writes.
The implications of this are immense. It means, quite simply, that one of the best ways to reduce greenhouse gases in the atmosphere is to move away from agriculture, which is based upon the destruction of forests and grasslands, and towards other means of subsistence. It means moving away from a way of life 10,000 years old. It means rethinking the entire structure of our food system – in some ways, the entire structure of our culture.
Some ambitious, visionary individuals are working in parallel with this strategy, racing against time to restore grasslands and to stabilize Earth’s climate.
In Russia, in the remote northeastern Siberian state of Yakutia, a scientist named Sergei Zimov has an ambitious plan to recreate a vast grassland – a landscape upon whom millions of herbivores such as mammoths, wild horses, reindeer, bison, and musk oxen fed and roamed until the end of the last ice age.
“In future, to preserve the permafrost, we only need to bring herbivores,” says Zimov. “Why is this useful? For one, the possibility to reconstruct a beautiful [grassland] ecosystem. It is important for climate stability. If the permafrost melts, a lot of greenhouse gases will be emitted from these soils.”
Zimov’s project is nicknamed “Pleistocene Park,” and stretches across a vast region of shrubs and mosses, low productivity communities called ‘Taiga’. But until 12,000 years ago, this landscape was highly productive pastures for a span of 35,000 years, hosting vast herds of grazers and their predators.
“Most small bones don’t survive because of the permafrost,” says Sergei Zimov. “[But] the density of skeletons in this sediment, here and all across these lowlands: 1,000 skeletons of mammoth, 20,000 skeletons of bison, 30,000 skeletons of horses, and about 85,000 skeletons of reindeer, 200 skeletons of musk-ox, and also tigers [per square kilometer].”
These herds of grazers not only supported predators, but also preserved the permafrost beneath their feet, soils that now contain 5 times as much carbon as all the rainforests of Earth. According to Zimov, the winter foraging behavior of these herbivores was the mechanism of preservation.
“In winter, everything is covered in snow,” Zimov says. “If there are 30 horses per square kilometer, they will trample the snow, which is a very good thermal insulator. If they trample in the snow, the permafrost will be much colder in wintertime. The introduction of herbivores can reduce the temperatures in the permafrost and slow down the thawing.”
In the Great Plains of the United States and Canada, a similar plan to restore the landscape and rewild the countryside has emerged. The brainchild of Deborah and Frank Popper, the plan calls for the gradual acquisition of rangelands and agricultural lands across the West and Midwest, with the eventual goal of creating a vast nature preserve called the Buffalo Commons, 10-20 million acres of wilderness, an area 10 times the size of the largest National Park in the United States (Wrangell-St. Elias National Park in Alaska).
In this proposed park, the Poppers envision a vast native grassland, with predators following wandering herds of American Bison and other grazers who follow the shifting grasses who follow the fickle rains. The shifting nature of the terrain in the Great Plains requires space, and this project would provide it in tracts not seen for hundreds of years.
In parts of Montana, the work has already begun. Many landowners have sold their farms to private conservation groups to fill in the gaps between isolated sections of large public lands. Many Indian tribes across the United States and Southern Canada are also working to restore Bison, who not only provide high quality, healthy, traditional food but also contribute to biodiversity and restore the health of the grasslands through behavior such a wallowing, which creates small wetlands.
Grasslands have the power to not only restore biodiversity and serve as a rich, nutrient-dense source of food, but also to stabilize global climate. The soils of the world cannot survive agricultural civilizations for much longer. If the plows continue their incessant work, this culture will eventually go the way of the Easter Islanders, the Maya, the Greeks, the Macedonians, the Harrapans, or the Roman Empire – blowing in the wind, clouding the rivers. Our air is thick with the remnants of ancient soils, getting long overdue revenge for their past mistreatment.
The land does not want fields. It wants Bison back. It wants grasslands, forests, wetlands, birds. It wants humans back, humans who know how to live in a good way, in relationship with the soil and the land and all the others. The land wants balance, and we can help. We can tend the wild and move towards other means of feeding ourselves, as our old ancestors have done for long years. It is the only strategy that takes into account the needs of the natural world, the needs for a land free of plows and tractor-combines.
In time, with luck and hard work, that ancient carbon will be pulled from the atmosphere – slowly at first, but then with gathering speed. The metrics of success are clear: a calmed climate, rivers running free, biodiversity rebounding. The task of achieving that success is a great challenge, but guided by those who believe in restoring the soil, we can undo 8,000 years of mistakes, and finally begin to live again as a species like any other, nestled in our home, at peace and in balance, freed at last from the burdens of our ancestors’ mistakes.
Climate meddling dates back 8,000 years. By Alexandra Witze. April 23rd, 2011. Science News. http://www.sciencenews.org/view/generic/id/71932/title/Climate_meddling_dates_back_8%2C000_years#video
Editor’s Note: While climate change is taken as THE pressing ecological concern of current era, biodiversity loss is the often less known but probably more destructive ecological disaster. UNEP estimates we lose 200 species in a day. That is 200 species that are never going to walk the Earth again. With these, we lose 200 creatures that play a unique and significant part in the natural communities, and immeasurable contributions of each to the health of the nature.
This study finds 69% average drop in animal populations since 1970. Over those five decades most of the decline can be traced to habitat destruction. The human desire for ever more growth played out over the years, city by city, road by road, acre by acre, across the globe. It is to want a new cell phone and never give a second thought as to where it comes from. Corporations want to make money so they hire the poor who want only to feed their families and they cut down another swath of rainforest to dig a mine and with it a dozen species we haven’t even named yet die. Think about what goes into a house to live in and the wood that must come from somewhere, and the coal and the oil to power it, and to power the cars that take people from there to the store to buy more things. And on and on, that is the American Dream.
Wildlife populations tracked by scientists shrank by nearly 70%, on average, between 1970 and 2018, a recent assessment has found.
The “Living Planet Report 2022” doesn’t monitor species loss but how much the size of 31,000 distinct populations have changed over time.
The steepest declines occurred in Latin America and the Caribbean, where wildlife abundance declined by 94%, with freshwater fish, reptiles and amphibians being the worst affected.
High-level talks under the U.N. Convention on Biological Diversity (CBD) will be held in Canada this December, with representatives from 196 members gathering to decide how to halt biodiversity loss by 2030.
In 2014, as temperatures topped 40° Celsius, or 104° Fahrenheit, in eastern Australia, half of the region’s black flying fox (Pteropus alecto) population perished, with thousands of the bats succumbing to the heat in one day.
This die-off is only one example of the catastrophic loss of wildlife unfolding globally. On average, wildlife populations tracked by scientists shrank by nearly 70% between 1970 and 2018, a recent assessment b WWF and the Zoological Society of London (ZSL) found.
“When wildlife populations decline to this degree, it means dramatic changes are impacting their habitats and the food and water they rely on,” WWF chief scientist, Rebecca Shaw, said in a statement. “We should care deeply about the unraveling of natural systems because these same resources sustain human life.”
WWF’s “Living Planet Report 2022,” launched this October, analyzed populations of mammals, birds, amphibians, reptiles and fish. “It is not a census of all wildlife but reports how wildlife populations have changed in size,” the authors wrote.
A million species of plants and animals face extinction today, according to a landmark 2019 report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), an international scientific body. The new analysis uncovers another aspect of this biodiversity crisis: The decline of wild populations doesn’t just translate into species loss but can also heighten extinction risk, particularly for endemic species found only in one location.
Instead of looking at individual species, the Living Planet Index (LPI) on which the report is based tracks 31,000 distinct populations of around 5,000 species. If humans were considered, for example, it would like tracking the demographics of countries. Population declines in one country could indicate a localized threat like a famine, but it was happening across continents, that would be cause for alarm.
The steepest species declines occurred in Latin America and the Caribbean, where wildlife abundance dropped by 94% on average. In this region, freshwater fish, reptiles and amphibians were the worst affected.
Freshwater organisms are at very high risk from human activities worldwide. Most of these threats are linked to habitat loss, but overexploitation also endangers many animals. In Brazil’s Mamirauá Sustainable Development Reserve, populations of Amazon pink river dolphin or boto (Inia geoffrensis) fell by 65% between 1994 and 2016. Targeted fishing of these friendly animals for their use as bait contributed to the decline.
Climatic changes render terrestrial habitats inhospitable too. In Australia, in the 2019-2020 fire season, around 10 million hectares (25 million acres) of forestland was destroyed, killing more than 1 billion animals and displacing 3 billion others. For southeastern Australia, scientists showed that human-induced climate change made the fires 30% more likely.
These losses are happening not just in land-based habitats but also out at sea. Coral reefs and vibrant underwater forests are some of the most threatened ecosystems in the world. But they’re being battered by a changing climate that makes oceans warmer and more acidic. The planet has already warmed by 1.2°C (2.2°F) since pre-industrial times, and a 2°C (3.6°F) average temperature rise will decimate almost all tropical corals.
However, the bat deaths in Australia, Brazil’s disappearing pink river dolphins, and the vulnerability of corals are extreme examples that can skew the index, which averages the change in population sizes. In fact, about half of wildlife populations studied remained stable and, in some cases, even grew. Mountain gorillas (Gorilla beringei beringei) in the Virunga Mountains spanning Rwanda, the Democratic Republic of Congo and Uganda number around 604 today, up from 480 in 2010.
Despite these bright spots, the overall outlook remains gloomy. Even after discounting the extremes, the downward trend persists. “After we removed 10 percent of the complete data set, we still see declines of about 65 percent,” Robin Freeman, an author of the report and senior researcher at ZSL, said in a statement.
Often, habitat loss, overexploitation and climate change compound the risk. Even in cases where a changing climate proves favorable, the multitude of threats can prove insurmountable. Take bumblebees, for example. Some species, like Bombus terrestris or the buff-tailed bumblebee, could actually thrive as average temperatures rise. But an assessment of 66 bumblebee species documented declining numbers because of pesticide and herbicide use.
The report emphasizes the need to tackle these challenges together. Protecting habitats like forests and mangroves can, for example, maintain species richness and check greenhouse gas emissions. The kinds of plants and their abundance directly impact carbon storage because plants pull in carbon from the atmosphere and store it as biomass.
One of the deficiencies of the LPI is that it doesn’t include data on plants or invertebrates (including insects like bumblebees).
The report was released in the run-up to environmental summits that will see countries gather to thrash out a plan to rein in climate change in November and later in the year to reverse biodiversity loss. Government leaders are set to meet for the next level of climate talks, called COP27, in Egypt from Nov. 6-13. At the last meeting of parties, known as COP26 in Glasgow, U.K., last year, nations committed to halt biodiversity loss and stem habitat destruction, partly in recognition that this would lower humanity’s carbon footprint.
In December, the 15th meeting of the Conference of the Parties to the U.N. Convention on Biological Diversity (CBD) will be held in Montreal. Representatives from 195 states and the European Union will meet to decide the road map to 2030 for safeguarding biodiversity.
Herbertsson, L., Khalaf, R., Johnson, K., Bygebjerg, R., Blomqvist, S., & Persson, A. S. (2021). Long-term data shows increasing dominance of Bombus terrestris with climate warming. Basic and Applied Ecology,53, 116-123. doi:10.1016/j.baae.2021.03.008
Herbertsson, L., Khalaf, R., Johnson, K., Bygebjerg, R., Blomqvist, S., & Persson, A. S. (2021). Long-term data shows increasing dominance of Bombus terrestris with climate warming. Basic and Applied Ecology,53, 116-123. doi:10.1016/j.baae.2021.03.008
Outhwaite, C. L., McCann, P., & Newbold, T. (2022). Agriculture and climate change are reshaping insect biodiversity worldwide. Nature,605(7908), 97-102. doi:10.1038/s41586-022-04644-x
Sobral, M., Silvius, K. M., Overman, H., Oliveira, L. F. B., Raab, T. K., & Fragoso, J. M. V. 2017. Mammal diversity influences the carbon cycle through trophic interactions in the Amazon. Nature Ecology & Evolution,1, 1670–1676. doi:10.1038/s41559-017-0334-0
Editor’s note: The dominant global culture (“industrial civilization”) is built on resource extraction and forced conversion of habitat to exclusive human use, and this has serious consequences.
Both global warming and the ongoing mass extermination of life on the planet (which has been deemed “the sixth mass extinction”), as well as other ecological crises (aquifer depletion, toxification of the total environment, ecosystem collapse, oceanic dead zones, etc.) are symptoms of humanity’s broken relationship to the planet. In plain terms: this way of life is killing the planet.
Today’s article reminds us that these crises are deeply interlinked, and so are solutions. While we are a revolutionary organization, every small step in the right direction also matters. And as a biocentric organization, we are in favor of actions to protect the natural world rather than putting our faith in technological Bright Green Lies.
Mass extinction lurks beneath the surface of the sea. That was the dire message from a study published in April in the journal Science, which found that continuing to emit greenhouse gases unchecked could trigger a mass die-off of ocean animals that rivals the worst extinction events in Earth’s history.
The findings serve as just the latest reminder that climate change and biodiversity loss are interconnected crises — even if they’re rarely addressed in tandem by policymakers.
Toward that point, the Science study came with a dose of hopeful news: Action to curb greenhouse gas emissions and keep warming below 2 degrees Celsius could cut that extinction risk by 70%.
Additional research published in Global Change Biology offers another encouraging finding. The study, by an international team of scientists, found that not only can we do better at addressing biodiversity issues — we can do it while also targeting climate change.
“Many instances of conservation actions intended to slow, halt or reverse biodiversity loss can simultaneously slow anthropogenic climate change,” the researchers wrote in the study.
Their work looked at 21 proposed action targets for biodiversity that will be the focus of this fall’s international convening of the Convention on Biological Diversity in Kunming, China — a meeting delayed two years by the COVID-19 pandemic. The researchers found that two-thirds of those biodiversity targets also support climate change mitigation, even though they weren’t explicitly designed for that goal. The best opportunities to work on these crises together were actions to avoid deforestation and restore degraded ecosystems. Of particular focus, the study found, should be coastal ecosystems such as mangroves, seagrass and salt marshes, which can store large amounts of carbon and support a diversity of animals.
A pelican enjoys a perch in a mangrove stand in the Galapagos. Photo: Hans Johnson (CC BY 2.0)
Also important is restoring forests and woodlands, but doing so with native species is critical. Planting monocultures of nonnative trees won’t boost biodiversity, the researchers point out, despite such endeavors being incentivized as a climate change solution.
Another target is reducing runoff into rivers, lakes and coastal waters from excess nutrients — including nitrogen and phosphorus — that cause algal blooms and oxygen-depleted waters. This eutrophication, combined with warming, may increase greenhouse gas emissions in freshwater bodies, in addition to harming fish and other animals.
Expanding and connecting the network of protected areas is another mutualistic target. Globally, we’ve protected about 15% of land and 7% of marine habitats. But we need to bump those numbers up considerably. As the researchers behind the Global Change Biology study put it, “There is a substantial overlap of 92% between areas that require reversing biodiversity loss and the areas needing protection for enhancing carbon storage and drawdown.”
Working on these issues in tandem can help boost the benefits.
We’re also spending large sums of money in all the wrong places. The study lists the reduction or elimination of subsidies that are harmful to biodiversity and the climate as “one of the most important and urgent reforms.”
We spend 10 times more on subsidies for environmentally harmful practices than on biodiversity conservation, the researchers note. Brazil, for example, spends 88 times more on subsidizing activities linked to deforestation than on those that may help stop it.
Other target areas to boost biodiversity and climate work include recovering and conserving wild species; greening urban areas; eliminating overfishing; reducing food and agricultural waste; and shifting diets to include more plant-based foods and less meat and dairy.
And, the researchers say, we need to “mainstream” the issues together — embedding both climate and biodiversity targets and metrics into policy, business and consumer practices.
Understanding these issues should start early, too. A study of school curricula in 46 countries found that fewer than half addressed climate change, and a paltry one-fifth referenced biodiversity. Both these subjects should be covered more and integrated together, the researchers say.
It’s not possible, after all, to tackle one crisis without addressing the other.
To fight climate change, we need fully functioning ecosystems with healthy populations of native plants and animals.
“And climate change is damaging this capacity,” said Hans-Otto Pörtner, a study coauthor and climate researcher at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research. “Only when we succeed in drastically reducing emissions from fossil fuels can nature help us to stabilize the climate.”