When you cut and burn a tropical forest, you’re left with a barren plain of cracked red mud, incapable of supporting life – the opposite of the teeming, hyperdiverse array of life that was destroyed. Once the trees are gone, the nutrients wash away and the soil degrades into a dense, brick-like layer so hardened that plant roots can’t get through it.
This was the vision of tropical deforestation held in the popular imagination for many years, but the reality is more complex – and more hopeful.
In recent decades, researchers have found that tropical forests are remarkably resilient. As long as some remnants are left when the forest is cleared to provide seeds and refuges for seed dispersers, tropical forests can grow back with astonishing speed.
In a paper published this week in Nature, lead author Lourens Poorter and a team of international collaborators, including me, found that forests in Central and South America can quickly rebound without human intervention on land that has been cleared for cattle grazing or growing crops.
This finding has important implications for climate change because these so-called secondary forests soak up large amounts of carbon from the atmosphere, even without costly reforestation efforts. These regenerating forests are also crucial for protecting biodiversity and all the ecological and social benefits it provides.
Tropical secondary forests – that is, forests that grow after a major clearing, such as a fire, farming or logging – cover an increasing part of the globe. And as their extent expands, so does their potential to shape conservation strategies, both at the local and global scales.
At the U.N. Climate Summit in 2014, 30 nations and a host of NGOs and private companies endorsed the New York Declaration on Forests, a document that advocates halving deforestation by 2020 and ending it completely by 2030.
One of the key points of the declaration calls for the restoration of 150 million hectares (about 375 million acres) of degraded forest land by 2020 and additional restoration in the following decade.
But active forest restoration can be an expensive process, and it may not be cost-effective or even necessary in every case. In landscapes with low levels of degradation, simply protecting young forests and allowing them to develop may be the best strategy.
In our research, my colleagues and I present the largest data set yet assembled to investigate forest regrowth in the New World tropics. The data set spans 45 sites in the lowland tropics from wet forest to dry forest, with a total of 1,478 plots and more than 168,000 individual trees.
It offers an unprecedented, and more hopeful, view of forest recovery.
According to this analysis, tropical secondary forests have enormous potential for removing carbon from the atmosphere. The net carbon uptake for these secondary forests is 11 times that of old-growth forests in the region we studied.
The rate of biomass recovery varies widely across the region, with the fastest regrowth in areas with high rainfall. The median time for a forest to reach 90 percent of old-growth biomass levels was 66 years, but recovery can be much faster in some areas.
It shouldn’t come as a surprise that tropical forests can grow back after major disturbances. Tropical forests can be affected by a number of different large-scale natural disasters like floods, fires, landslides, major storms and volcanic eruptions.
Even old-growth tropical forests are highly dynamic systems, marked by cycles of tree death and regrowth. The mortality rates for trees larger than 10 centimeters in diameter have been estimated at one percent to two percent per year for forests in the Amazon and Central America. In other words, at the upper end, one in every 50 large trees will fall in the course of a given year.
The gaps in the forest that result from treefalls are rapidly colonized by a riot of vines and fast-growing tree saplings. The heterogeneity of habitats produced by this cycle is a major driver of tropical diversity.
In addition, the history of human-induced disturbances in tropical forests is longer and more complex than we often acknowledge.
Legacies of ancient human use, stretching back for millennia, have been detected in nearly every “pristine” tropical forest on earth: massive earthworks in the Amazon and modern-day Cambodia; charcoal and pottery fragments in the Congo Basin; and evidence of forest clearing going back nearly 50,000 years in Papua New Guinea.
Indeed, various forms of slash-and-burn cultivation have been practiced for millennia throughout the tropics.
As long as the cleared areas are modest in size and the period between cycles of cultivation is sufficient for recovery, diverse forests can persist for thousands of years.
Tropical secondary forests can – and should – form a substantive part of the long-term global strategy to combat carbon emissions and preserve biodiversity for the future.
Our recent research shows, for example, that in areas where biomass recovery is slow – like the tropical dry forest – we should prevent further forest loss. Where recovery is rapid, we can combine old-growth forest conservation with policies that promote secondary forest formation.
Shifting focus to the conservation of regenerating forests should not take away from the urgent imperative to conserve the remaining uncut tropical forest.
The clearing of old-growth tropical forests is a major source of human-induced greenhouse gas emissions, second only to fossil fuel combustion. Clearly, keeping the carbon that’s currently stored in intact tropical forests from being released to the atmosphere should be a priority.
Old-growth tropical forests also harbor immense biological diversity – including genetic diversity – and if all of the remaining old-growth forests in a landscape are cut, there will be no seed source to promote regeneration.
Conserving secondary forests offers a different, and complementary, set of benefits.
As well as their massive potential for taking up carbon as they grow, secondary forests provide resources and livelihoods for the people who inhabit them.
Secondary forests can harbor a high diversity of ethnobotanically important species that can be used for medicines. They can serve as extractive reserves, where limited harvesting of timber, game animals and other forest products will prevent the exploitation of resources in vulnerable protected areas. They protect watersheds and prevent erosion.
As secondary forests grow back, they eventually come to resemble the forest that was cut, and in the meantime, they knit together the remaining fragments of forest into a more contiguous landscape.
As David Quammen wrote in “Song of the Dodo (1997),” isolated populations of organisms in forests lose connections to the resource base that supports them. Over generations they lose their genetic diversity, making them more vulnerable to inbreeding, disease, and eventual extinction.
Secondary forests offer the hope of reconnecting habitats and creating a more resilient landscape for the future.
So harnessing the power of forest regeneration in the tropics will have benefits both locally – providing resources and restoring ecosystem services – and globally, by sequestering carbon from the atmosphere.
At the Paris Climate Summit, leaders took important steps toward halting deforestation. Promoting forest regrowth is another vital piece of the equation. It’s time for policymakers to recognize the benefits that tropical secondary forests provide, and to shape policies that take advantage of this enormous potential.
An alarming new study has shown that the world’s forests are not only disappearing rapidly, but that areas of “core forest” — remote interior areas critical for disturbance-sensitive wildlife and ecological processes — are vanishing even faster.
Core forests are disappearing because a tsunami of new roads, dams, power lines, pipelines and other infrastructure is rapidly slicing into the world’s last wild places, opening them up like a flayed fish to deforestation, fragmentation, poaching and other destructive activities.
Most vulnerable of all are forests in the tropics. These forests sustain the planet’s most biologically rich and environmentally important habitats.
The collapse of the world’s forests isn’t going to stop until we start to say “no” to environmentally destructive projects.
Those who criticise new infrastructure projects are often accused of opposing direly needed economic development, or — if they hail from industrial nations — of being hypocrites.
But when one begins to look in detail at the proposed projects, an intriguing pattern appears: Many are either poorly justified or will have far greater costs than benefits.
For example, in a recent essay in the journal Science, Amazon expert Philip Fearnside argues that many of the 330-odd hydroelectric dams planned or under construction in the Amazon will be more trouble than they’re worth.
Many of these dams will have huge environmental impacts, argues Fearnside, and will dramatically increase forest loss in remote regions.
This happens both because the Amazon is quite flat, requiring large areas of forest to be flooded, and because dams and their power lines require road networks that open up the forest to other human impacts. For instance, the 12 dams planned for Brazil’s Tapajós River are expected to increase Amazon deforestation by almost 1 million hectares.
Furthermore, Fearnside argues, much of the electricity the Amazon dams produce will be used for smelting aluminium, which provides relatively little local employment.
Fearnside asserts that mega-dams planned for the Congo Basin and Mekong River will also cause big problems, with limited or questionable benefits.
The explosive expansion of roads into the world’s last wild places is an even more serious problem. Indeed, Eneas Salati, one of Brazil’s most respected scientists, once quipped that “the best thing you could do for the Amazon is to blow up all the roads”.
Current projections suggest that by 2050, we’ll have nearly 25 million kilometres of additional paved roads — enough to encircle the Earth more than 600 times.
I have led three major studies of planned road expansion, for the entire planet and for the Brazilian Amazon and sub-Saharan Africa. All three show that many planned roads would have massive impacts on biodiversity and vital ecosystem services while providing only sparse socioeconomic benefits.
In Africa, for example, our analyses reveal that 33 planned “development corridors” would total over 53,000 kilometers in length while crisscrossing the continent and cutting into many remote, wild areas. Of these, we ranked only six as “promising” whereas the remainder were “inadvisable” or “marginal”.
There is a very active coalition of pro-growth advocates — including corporate lobbyists, climate-change deniers, and die-hard proponents of “economic growth” — that immediately decry any effort to oppose new developments.
Added to this are those who argue reasonably for economic development to combat poverty and disparity in developing nations. Such advocates often assert that an added bonus of development is greater sustainability, because impoverished people can be highly destructive environmentally. The denuded nation of Haiti is one such example.
Yet the on-the-ground reality is often far more complex. For instance, the heavy exploitation and export of natural resources, such as minerals, fossil fuels or timber, can cause nations to suffer “Dutch Disease” — an economic syndrome characterised by rising currency values, economic inflation and the weakening of other economic sectors, such as tourism, education and manufacturing.
Dutch Disease tends to increase economic disparity, because the poor are impacted most heavily by rising food and living costs. Further, the national economy becomes more vulnerable to economic shocks from fluctuating natural-resource prices or depletion. The Solomon Islands — which relies heavily on timber exports that are collapsing from overexploitation — is a poster-child for Dutch Disease.
On top of this is the toxic odour of corruption that pervades many big infrastructure projects. One would need an abacus just to keep track of the allegations.
To cite just two recent examples: in Malaysia, an independent investigation has concluded that nearly US$4 billion was misappropriated from a state-owned fund set up to attract international property, infrastructure and energy investments. And in Brazil, the granting of contracts for major Amazon dams has been drowning in allegations of corruption.
In both nations, public coffers needed for education, health and other vital services appear to have been hugely defrauded.
The bottom line is that many big infrastructure projects are being pushed by powerful corporations, individuals or interests that have much to gain themselves, but often at great cost to the environment and developing societies.
Globally, the path we’re currently following isn’t just unsustainable. It’s leading to an astonishingly rapid loss of forests, wildlife and wilderness. From 2000 to 2012, an area of forest two and half times the size of Texas was destroyed, while a tenth of all core forests vanished.
If we’re going to have any wild places left for our children and grandchildren, we simply can’t say “yes” to every proposed development project.
For those that will have serious environmental and social consequences, we need to start saying “no” a lot more often.
The past year has been a momentous time for the world’s forests, with both good and bad news. Fasten your seat belts, because 2016 promises to be another roller-coaster ride.
Here I hightlight five factors that could have a big impact on forests this year. For further discussion, see this insightful analysis by environmental journalist Rhett Butler.
The ripple effects from China’s slowing economy could be huge for forests. China has been an aggressive driver of mineral, fossil fuel and timber exploitation, especially in developing nations across the Asia-Pacific, Latin America, Africa and Siberia. It has pushed hard for road and infrastructure expansion into many remote wilderness regions — projects that have often opened a Pandora’s box of environmental problems for forests and wildlife.
With prices for many natural resources falling, forests could get some respite in 2016. Conservationists need to use this breathing space to create new protected areas and promote land-use planning in environmentally critical regions.
Africa, in the midst of a mining and road-building frenzy, is a particularly high priority.
The fire-breathing “Godzilla” drought ain’t dead yet — far from it. The unusual Pacific Ocean conditions feeding this monster are still strong. This could lead to serious droughts and fires in South and Central America and the Asia-Pacific region.
Indonesia, in particular, has been reeling from the drought, with massive forest and peat fires that have had much of Southeast Asia gasping for air. On a daily basis, Indonesia’s fires belched out as much carbon as the entire US economy.
If China’s economy is cooling off, then Brazil’s once-promising economy is entering an Ice Age — a remarkable downturn for a nation so rich in land and natural resources.
It’s hard to predict how this could affect rainforests like the vast Brazilian Amazon and the critically imperilled Brazilian Atlantic Forest, a global biodiversity hotspot that has been massively reduced and fragmented.
On the one hand, Brazil’s currency, the real, has fallen dramatically in value. That means that its export commodities such as timber, soy, beef, oil and minerals will be more competitive internationally — potentially promoting more forest exploitation.
On the other hand, domestic and international investors tend to be cautious in a slowing economy. New infrastructure and land-exploiting projects, such as a slate of planned mega-dams in the Amazon and elsewhere, may well slow down.
It’s hard to call this one. The imploding economy may well lead to the political demise of Brazilian President Dilma Rousseff, who generally has been pro-environment.
For instance, Rousseff did everything she could to staunch recent efforts to weaken Brazil’s Forest Code — a legal framework that’s been crucial for protecting the nation’s forests. Over the last decade, annual deforestation rates in the Brazilian Amazon have fallen by more than 75%, but rural and industrial lobbies have incessantly attacked the government land-use controls that have helped make this reduction possible.
A remarkable development in the last two years is that scores of corporations producing or using oil palm, wood pulp, soy, beef and other commodities have declared their intent to halt or sharply curtail forest destruction. Pressures from eco-conscious consumers and environmental NGOs have been a key driver of this trend.
Overall, this has been a hugely positive step. However, Indonesia and Malaysia — which collectively produce around 85% of all the world’s palm oil — appear determined to stop or erode zero-deforestation agreements for corporations working there.
Bottom line: they want to continue clearing large expanses of native forest for oil palm and industrial wood-pulp plantations, and the zero-deforestation agreements are getting in the way of this. Indonesia alone plans to fell another 14 million hectares of native forest by 2020.
This is truly a critical issue to watch. If corporations start to backslide on their zero-deforestation agreements, then conservationists are likely to let them know — loudly and emphatically — that they’re doing the wrong thing.
I attended the recent Climate Convention in Paris, where there were two key developments relating to forests.
Firstly, a formal agreement for advancing REDD — which stands for “reducing emissions from deforestation and forest degradation” — was finally approved.
In theory, this means that more international funding should start flowing for forest conservation — to slow deforestation, encourage forest regeneration and promote more-sustainable logging — all in the interest of reducing carbon emissions and thereby limiting global warming.
There’s no question that this is good news — though it’s time to stop talking and start acting.
In particular, wealthier nations such as the US, Japan and Australia must amp up their funding for REDD initiatives, especially in the tropics.
Secondly, the world’s nations agreed in principle to limit global warming to 2℃ — and to strive for an increase of just 1.5℃. It’s wonderful that nations have made this broad commitment, but actually achieving it is going to be a tremendous challenge.
There’s no time for complacency. The Paris Agreement will only be effective if it’s followed by concerted actions by nations to reduce their carbon emissions and conserve forests.
Conserving and regenerating forests really is one of the smartest things we can do for our planet’s health.
For one thing, protecting large expanses of forest makes these biodiversity-rich ecosystems much more resilient to future climate change.
Forest tracts that span large gradients in rainfall, elevation and other environmental factors give species the opportunity to migrate or find local refuges during heat waves, fires, storms and other extreme weather conditions.
Protecting and regenerating forests could also have a huge impact on the global climate. Forests cool the Earth’s surface while emitting trillions of tonnes of water vapour that generates much of the planet’s rainfall.
But most of all, forests can rapidly absorb and store a great deal of carbon. It has recently been estimated that a concerted effort to halt tropical deforestation and regenerate forests on degraded tropical lands could get us halfway to our global goal to reduce carbon emissions over the next 50 years.
As we follow the dramatic events unfolding for the world’s forests in 2016, we should bear in mind just how vital these imperilled ecosystems are for all of us.