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Tropical forests can regenerate in just 20 years without human interference

Tropical forests can regenerate in just 20 years without human interference

Study finds natural regrowth yields better results than human plantings and offers hope for climate recovery

Tropical forests can bounce back with surprising rapidity, a new study published today suggests.

An international group of researchers has found that tropical forests have the potential to almost fully regrow if they are left untouched by humans for about 20 years. This is due to a multidimensional mechanism whereby old forest flora and fauna help a new generation of forest grow – a natural process known as “secondary succession”.

These new findings, published in Science, could play an important role in climate-breakdown mitigation and provide actionable advice on how to act next. They also suggest that it is not too late to undo the damage that humanity has done through catastrophic climate change over the last few decades.

“That’s good news, because the implication is that, 20 years … that’s a realistic time that I can think of, and that my daughter can think of, and that the policymakers can think of,” said Lourens Poorter, professor in functional ecology at Wageningen University in the Netherlands and lead author of the paper.

This idea of natural regeneration is frequently disregarded in favour of tree plantations, but according to Poorter, the former yields better results than restoration plantings. “Compared to planting new trees, it performs way better in terms of biodiversity, climate change mitigation and recovering nutrients.”

The takeaway message is that we don’t necessarily need to plant more trees when nature is doing it by itself, Poorter said.

For this study, more than 90 researchers from all over the world came together to analyse exactly how tropical forest regrowth takes place. They pored over data about forest recovery from three continents, 77 sites and 2,275 plots of land in the Americas and West Africa. From there, they evaluated 12 specific criteria, such as the soil, plant functioning, ecosystem structure and biodiversity, and more. They then modelled this data – without which they would have had to wait for over 100 years to see this happen in the real world – with a technique called chronosequencing, allowing them to infer long-term trends in forest recovery.

The researchers looked in particular at what happens to tropical forest land that has been used for agriculture or farming and is then abandoned after a couple of seasons. They found that the old forest portion – including some fertile soil, any residual trees, seed banks and maybe stumps that can resprout – created a nourishing, interconnected ecosystem for new forest to start to grow.

The researchers found that different aspects take, respectively, more or less time to recover to the levels of “old forest” before it was used. Soil takes an average of 10 years to recover to its previous status, plant community and animal biodiversity take 60 years, and overall biomass takes a total of 120, according to their calculations.

But overall, tropical forests can get back to roughly 78% of their old-growth status in just 20 years. “That’s tremendously fast – surprisingly fast,” Poorter said.

Of course, these are just calculations, and one of the constraints of chronosequence-based analyses is that every location analysed is assumed to have the same history and successional dynamics, said Eric Salas, a researcher in geospatial sciences at Central State University who was not involved in this study. So there can be some misinterpretation.

“But understanding how secondary forests emerge naturally on abandoned agricultural lands is critical for ensuring biodiversity conservation,” Salas said, “particularly in tropical settings, where forests have complex structure and flora and fauna species are diverse.”

Related post:

The sun sets as smoke from illegal fires an area of Amazon rainforest lingers, south of Novo Progresso in Para state, Brazil, on August 15, 2020. (Photo by CARL DE SOUZA / AFP) (Photo by CARL DE SOUZA/AFP via Getty Images)


Logging and land conversion for agriculture has wiped out 34 per cent of the world’s original old-growth tropical rainforests and degraded another 30 per cent, leaving them more vulnerable to fire and future destruction.

The findings could be crucial for climate mitigation action in the future.

“For example, the secondary forests are like teenagers. They soak up carbon like crazy and they empty your fridge,” Poorter said. “If you look at old people, they consume very little, and it’s the same as the old growth forest.”

“What we want to advocate is: ‘Please value those secondary forests, and in areas where you can, please let those forests regrow back again naturally,” Poorter said. He mentions that a lot of the promises that have been made about planting trees in order to restore forests across the world are unrealistic. Most of the time, 30%-50% of those trees die, and they only pertain to a couple of species that cannot mimic the natural biodiversity of forests, according to Poorter.

“My plea is to use natural regrowth where you can and plant actively and restore actively where you need to. There’s a case-by-case approach, and this all depends on the local conditions and also on the local needs of the people because they live in these landscapes.”


Sofia Quaglia at The Guardian

Ghost forests creep up U.S. East Coast

Ghost forests creep up U.S. East Coast

New Jersey’s Atlantic white cedar forests are turning from green to a pale white, a sign of creeping sea levels and more frequent superstorms.

Shawn LaTourette sees a warning on the coast of New Jersey in the miles of Atlantic white cedar trees that have devolved into what researchers call ghost forests. 

It’s a term that points to the visceral changes of the landscape — going from lush green to a pale white — and the destruction of the area’s crucial role as a biodome and coastal buffer. These once-thriving forests are a direct result of climate change as the trees are suffocated by saltwater intrusion sparked by sea level rise and an uptick of hurricanes and superstorms.  

“If we pay close attention to our environment, we often see that it sends us signals,” LaTourette, the state’s commissioner of environmental protection, said while walking along a ghost forest spanning more than 300 acres in southern New Jersey. “This is a signal about that risk that we all face from saltwater intrusion from storm surge.”

Climate change is causing whole forests to die, like this one in New Jersey. The Atlantic White Cedar is particularly vulnerable to changes in the environment like salt water intrusion from storm surges and sea level rise.
Climate change is causing whole forests to die, like this one in New Jersey. The Atlantic White Cedar is particularly vulnerable to changes in the environment like salt water intrusion from storm surges and sea level rise. New Parks and Forestry

The Atlantic white cedar forests are seen as the first line of defense on New Jersey’s coast. They thrive in freshwater wetlands — swamps so thick that extreme caution and a good pair of wader boots are necessary in order to walk through them. As sea levels rise, these trees are hit first, and the saltwater intrusion is killing them due to their sensitive nature. That water will then move on to inundate farm fields, peoples’ homes, drinking water and businesses.

Along much of the Eastern Seaboard, the once-healthy coastal woodlands are dwindling rapidly — to the extent that if the rate of decline continues, these forested wetlands will reach the “point of no return within the century,” according to  University of Virginia and Duke University researchers focused on studying the ecosystems. Ghost forests are already a problem all along the East Coast and in states along the Gulf Coast, such as Louisiana, Mississippi and Alabama.

Coastal woodlands like these are critical ecosystems in the United States, as they filter pollutants, act as natural barriers and store carbon in the ground. But their positioning on the coast puts them at the vanguard of rising sea levels brought on by the warming atmosphere, therefore worsening some of the effects of climate change.

Forests are dying up and down the East Coast and along the Gulf Coast due to climate change. Researchers are studying trees like these at the Alligator River in North Carolina that are forming ghost forests.
Forests are dying up and down the East Coast and along the Gulf Coast due to climate change. Researchers are studying trees like these at the Alligator River in North Carolina that are forming ghost forests.Marcelo Ardon / North Carolina State University

“To be able to look at these forests and see that this is a direct result from climate change is frightening,” says Kristin Meistrell, a Stewardship Project director for the New Jersey Audubon Society, which focuses on environmental awareness and conservation. Meistrell has worked here for nearly  10 years and recalls walks she used to take on the property when she  started in 2012, surrounded by live Atlantic white cedar trees. Since then, she’s watched the forests completely die off.

“I think every community, every resident, every business has to ask itself hard questions.”


The state and environmental groups are scrambling to restore the cedar species in environments that aren’t as immediately threatened by impending storm surges. Foresters and environmental groups are largely focused on restoring forests in new homes, where they won’t be hit by sea level rise. The groups have cleared out large swaths of land typically filled with other hardwoods like maple, to allow remaining healthy cedars to drop seeds naturally with adequate space and access to sunlight. The New Jersey Audubon Society leverages farmers’ and hunters’ attachment to the land, working with them on their private property to develop forest stewardship plans to manage the property for wildlife like these cedars. 

“We’re trying to put this forest type back on the landscape,”  State Forester John Sacco said. “When we do that, we’re introducing biodiversity. There are suites of organisms that occur with this forest type that you really don’t find in other forests. It increases biodiversity, helps with resiliency, and it’s part of our natural heritage that we need to keep around and bequeath to the next generation.” 

This will take some time. A healthy cedar forest will take decades to develop, and they’re playing catch up after losing more than 80 percent of the woodlands due to logging over the last two centuries. 

Trees like the Atlantic White Cedar were decimated in the past centuries mostly due to logging for construction.
Trees like the Atlantic White Cedar were decimated in the past centuries mostly due to logging for construction. Only about 20,000 acres of Atlantic White Cedar remain in New Jersey from the 125,000 acres at the time of European settlement. New Jersey Parks and Forestry

Growing new trees in safer homes is just one conservation method in their toolbox, as New Jersey and other states also focus on protecting what already exists. The Nature Conservancy works on refuges along the Outer Banks in North Carolina, where it is building oyster reefs and ditch networks to slow down erosion and control water running upstream, and adding more vegetation that can tolerate salt water into the peat soils where the trees typically grow, making root systems more sturdy. 

The scientists from University of Virginia and Duke project that coastal forested wetlands will be “drowned and salted out of existence through the North American Coastal Plain within 100 years,” but also note this isn’t the only region globally that’s at risk. Environments in Brazil, Ukraine and Mozambique have similar wetland ecosystems, but don’t currently have research available. 

“I think every community, every resident, every business has to ask itself hard questions,” LaTourette said, “about whether it is positioned to confront the ravages of climate change.”


Andrew Bossone and Maura Barrett at NBC News

On the Web This Week, 18 October

On the Web This Week, 18 October

On the web this week, a Forest Of The Future planted in Johannesburg, are electric vehicles better for SA, and scientists use drones to save sacred trees in Hawaii.

 Last month, in celebration of their 100th birthday, KLM Royal Dutch Airlines, together with 14 456 scholars across Gauteng, broke the record for the most number of paper planes flown at a single time.

14 456 paper planes, each containing a message from ordinary South Africans dedicated to their future selves, were launched at 15 schools across the province. Now, the brand has taken those paper planes and used them as compost for a new ‘Forest of the Future’ initiative which has been unveiled at the Mother of Peace orphanage situated in Northriding, Johannesburg.

Picture credit: Berea Mail

AROUND 60 walkers left uShaka Pier on Saturday on an intrepid 150km seven-day adventure from Durban to Mtunzini, on the KZN north coast, to raise awareness of the province’s pristine coastline while also addressing the plastic threat to our oceans.

The participants, who were all part of the Philocaly Trail (‘Philocaly’ meaning The Love of Beauty) joined Berea resident, Nikki Williamson, the force behind the initiative and passionate lover of nature, the ocean and our natural heritage on the epic journey.

Picture credit: 123RF/Bunlue Nantaprom

SA’s submission to the Paris agreement on climate change says the country will have more than 2.9-million electric vehicles (EVs) on the road by 2050, with R6.5-trillion to be invested in the industry over the next four decades.

That is a significant sum of money for a country with failing parastatals, which include its electricity supplier, Eskom. This raises the question: is it practical for SA to commit to investing this amount in electric vehicles within the next four decades?

Picture credit: UH Hilo SDAV Laboratory

In early September, a drone flew over the Waiakea Forest Reserve on Hawaii’s Big Island. It slowed its pace, lowered itself to a hover just feet from the canopy, and readied a device attached to its undercarriage. Two plastic “arms” rotated gently, grabbed a small branch, and, using a built-in saw, chopped it off. Having collected the sample, the drone flew away.

This could be the future of forestry. The operation, conducted by Ryan Perroy, a geographer at the University of Hawaii at Hilo, is part of a rescue mission to save a special tree — the sacred ʻŌhiʻa (pronounced “oh-HEE-ah”) that blankets Hawaii’s islands. For many Hawaiians, the ʻŌhiʻa is a symbol of nature, an ecological backbone, and the very essence of the forest. But the trees are under attack.

Picture credit:  David Tipling Getty Images

Scientists are discovering that the Arctic’s rising temperatures might be the second-biggest threat to wildlife.

Climate variability is increasing, as well, meaning once-rare extreme events like flash floods and droughts happen more often. It’s difficult for wildlife to cope with these pulses; animals have responded to global warming by shifting ranges and behaviors, but these dramatic changes can come too quickly for adaptation.

This is part one in a six-part documentary series on global cities and the development of urban networks as the emerging geography of connectivity in an age of globalization. Produced by: systemsinnovation.io

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