How would planting 8 billion trees every year for 20 years affect Earth’s climate?

Planting 8 billion trees a year would replace about half of the 15 billion cut down annually.
Michael Tewelde/AFP via Getty Images

Karen D. Holl, University of California, Santa Cruz

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

If we planted 8 billion trees a year for 20 years, what would happen on Earth? – Shivam K., age 14, Nawada, Bihar, India

Politicians, business leaders, YouTubers and celebrities are calling for the planting of millions, billions or even trillions of trees to slow climate change.

There are currently almost 8 billion people on Earth. If every single person planted a tree each year for the next 20 years, that would mean roughly 160 billion new trees.

Could massive tree planting actually slow climate change?

Trees and carbon

Carbon dioxide is the main gas that causes global warming. Through photosynthesis, trees and other plants transform carbon dioxide from the atmosphere into carbohydrates, which they use to make stems, leaves and roots.

The amount of carbon a tree can store varies a great deal. It depends on the tree species, where it is growing and how old it is.

Let’s say the average tree takes up 50 pounds of carbon dioxide a year. If a person planted a tree every year for 20 years – and each one survived, which is highly unlikely – those 20 trees would take up about 1,000 pounds, or half a ton, of carbon dioxide per year.

The average person in the United States produces a whopping 15.5 tons of carbon dioxide a year compared with 1.9 tons for an average person in India. This means that if each person in the U.S. planted one tree per year it would offset only about 3% of the carbon dioxide they produce each year, after all 20 trees had matured. But, it would offset 26% for somebody in India.

Planting trees is certainly part of the solution to climate change, but there are more important ones.

Aerial view of patchwork deforestation of rainforest. — Clearing the Amazon rainforest for livestock farms in Brazil in 2017.
Brazil Photos/LightRocket via Getty Images

Protecting the trees we have

There are about 3 trillion trees on Earth, which is only half as many as 12,000 years ago, at the start of human civilization.

People cut down an estimated 15 billion trees each year. A lot of those trees are in tropical forests, but deforestation is happening all over the planet.

Protecting existing forests makes sense. Not only do they absorb carbon dioxide in the trees and the soil, but they provide habitat for animals. Trees can provide firewood and fruit for people. In cities, they can offer shade and recreational spaces.

But trees should not be planted where they didn’t grow before, such as in native grasslands or savannas. These ecosystems provide important habitat for their own animals and plants – and already store carbon if they are left undisturbed.

Doing more

To slow climate change, people need to do much more than plant trees. Humans need to reduce their carbon dioxide and other greenhouse gas emissions quickly by transitioning to renewable energy sources, like solar and wind. People should also reduce the amount they drive and fly – and eat less meat, as meat has a much larger carbon footprint per calorie than grains and vegetables.

It is important that everybody – businesses, politicians, governments, adults and even kids – do what they can to reduce fossil fuel emissions. I know it can seem pretty overwhelming to think about what you as one person can do to help the planet. Fortunately, there are many options.

Volunteer with a local conservation organization, where you can help protect and restore local habitats. Discuss with your family new lifestyle choices, like biking, walking or taking public transit rather than driving.

Two Girl Scouts take a stand against deforestation.

And don’t be afraid to lead an effort to protect trees, locally or globally. Two 11-year-old Girl Scouts, concerned about the destruction of rainforests for palm oil plantations, led an effort to eliminate palm oil in Girl Scout cookies.

Sometimes change is slow, but together people can make it happen.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Karen D. Holl, Professor of Restoration Ecology, University of California, Santa Cruz

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Planning to plant an Australian native like wattle? Read this first — you might be spreading a weed

Coastal wattle.
Dr David Chael, Author provided

Singarayer Florentine, Federation University AustraliaAustralian native plants are having a moment in the sun, with more of us seeking out and planting native species than in the past. Our gardens — and our social media feeds — are brimming with beautiful Australian native blooms.

But not all Australian native species belong in all Australian environments. In fact, many have become pests in places far from their original homes.

They can crowd out other native endemic species, affect the local balance of insects and other animals, wreck soils and even increase fire risk.

Here are three Australian native plants that have become invasive species after ending up in places they don’t belong.

Sydney golden wattle (Acacia longifolia subspecies longifolia)

Originally extending from East Gippsland in Victoria up about as far as Brisbane in Queensland, this species is undoubtedly photogenic. It’s also an invasive weed in parts of Victoria, South Australia and Western Australia.

It was spread across the nation by well-meaning gardeners who saw it as a charming ornamental plant. However, its seeds made their way into the wild and took off — it’s what’s known in my field as “a garden escapee”.

Like many weeds, this species can capitalise on a natural disaster; after fire it can send out shoots from its base. Acacias are often one of the first species to sprout following a bushfire. They’re now completely dominant and spreading in many areas.

Sydney golden wattle is an invasive weed in other parts of Victoria, South Australia and Western Australia.
Gill Armstrong, Author provided

Seeds of Sydney golden wattle can last in the soil for many decades, long after the parent plants have died. The heat from a fire cracks the hard seed coat, allowing water to enter and germination to take off.

In the Grampians, in Victoria, Sydney golden wattle is causing terrible soil problems. Many native plants endemic to this area don’t like high levels of soil nitrogen, but Acacia longifolia subsp. longifolia is a nitrogen-fixing plant.

Acacia longifolia subsp. longifolia has quite long, thin seed pods.
Gill Armstrong, Author provided

In other words, it increases the nitrogen in the soil and changes the soil nutrient status and even physical aspects of the soil. It can grow tall and produce a lot of foliage, which reduces the amount of light coming to the ground. That makes it harder for native species lower to the ground to survive.

This is a major challenge, especially in biodiversity-rich places like the Grampians.

Coast wattle (Acacia longifolia subspecies sophorae)

The blooms on Acacia longifolia subspecies sophorae (Coast wattle) look more or less the same as many other wattles, but the leaves are a bit shorter and stubbier.

Originally, Coast wattle occurred along the east coast from western Victoria — up about as far as Brisbane and down south as far as Tasmania (where Sydney golden wattle did not occur naturally).

_Acacia longifolia subsp. sophorae_, also known as 'Coastal Wattle', has shorter, stubby leaves. — Acacia longifolia subsp. sophorae, also known as ‘Coastal Wattle’, has shorter, stubby leaves.
Tatters ✾/Flickr, CC BY

It was originally restricted to sandy sites at the top of beaches but has been deliberately planted as a “sand-binder” in other sites. It’s also naturally spread into heathlands inland of the beaches and is now causing huge problems around our coasts.

Like the earlier example, it dominates local ecosystems and displaces native species endemic to the area (particularly in our species-rich heathlands), which affects local insect habitats. It is also now modifying natural sand dune patterns.

It is increasing fire risk by changing heathland plant profiles from mostly short shrubs of limited bulk to tall, dense shrublands with much higher fuel levels.

Coast teatree (Leptospermum laevigatum)

As with Coast wattle, Coast teatree was formerly restricted to a narrow strip on sandy soils just above the beaches of south-eastern Australia. But it has now spread into nearby heathlands and woodlands. It’s even reached as far as Western Australia.

This teatree plant is now considered an invasive species in parts of Victoria and South Australia.

Although the mature plants are usually killed by fire, the seeds are abundant and very good at surviving; they pop out of their capsules after fires.

Coast teatree produces a lot of seeds.
Dr David Chael, Author provided

They are high-density plants that burn quickly in a fire. They are very quick to take over and push out endemic species.

For example, parts of the Wilson’s Prom National Park in Victoria, which was originally a Banksia woodland, have now been converted almost to a teatree monoculture. It is very sad.

A call to action

Authorities are trying their best to keep these and other native invasive species under control, but in some cases things may never go back to the way they were. Sometimes, the best you can hope for is just to strike a balance between native and invasive species.

When you do landcare restoration work or home gardening, I urge you to look up the plant history and see if the species you’re thinking of planting is listed as one that might cause problems in future.

When you go to purchase from a nursery or plant centre, be cautious. Think twice before you bring something into your garden. Too many species have “jumped the garden fence” and now cost us a great deal in control efforts and in native species loss.

Lots of apps, such as PlantNet, can help you identify plants and see what is native to your area.

Australia has spent billions trying to control invasive species and environmental weeds. Anything you can do to help is a bonus.

Singarayer Florentine, Professor (Restoration Ecologist), Federation University Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Planting non-native trees accelerates the release of carbon back into the atmosphere

Lauren Waller and Warwick Allen, University of Canterbury

Large-scale reforestation projects such as New Zealand’s One Billion Trees programme are underway in many countries to help sequester carbon from the atmosphere.

But there is ongoing debate about whether to prioritise native or non-native plants to fight climate change. As our recent research shows, non-native plants often grow faster compared to native plants, but they also decompose faster and this helps to accelerate the release of 150% more carbon dioxide from the soil.

Our results highlight a challenging gap in our understanding of carbon cycling in newly planted or regenerating forests.

It is relatively easy to measure plant biomass (how quickly a plant grows) and to estimate how much carbon dioxide it has removed from the atmosphere. But measuring carbon release is more difficult because it involves complex interactions between the plant, plant-eating insects and soil microorganisms.

This lack of an integrated carbon cycling model that includes species interactions makes predictions for carbon budgeting exceedingly difficult.

How non-native plants change the carbon cycle

There is uncertainty in our climate forecasting because we don’t fully understand how the factors that influence carbon cycling – the process in which carbon is both accumulated and lost by plants and soils – differ across ecosystems.

Carbon sequestration projects typically use fast-growing plant species that accumulate carbon in their tissues rapidly. Few projects focus on what goes on in the soil.

Non-native plants often accelerate carbon cycling. They usually have less dense tissues and can grow and incorporate carbon into their tissues faster than native plants. But they also decompose more readily, increasing carbon release back to the atmosphere.

Our research, recently published in the journal Science, shows that when non-native plants arrive in a new place, they establish new interactions with soil organisms. So far, research has mostly focused on how this resetting of interactions with soil microorganisms, herbivorous insects and other organisms helps exotic plants to invade a new place quickly, often overwhelming native species.

Invasive non-native plants have already become a major problem worldwide, and are changing the composition and function of entire ecosystems. But it is less clear how the interactions of invasive non-native plants with other organisms affect carbon cycling.

Planting non-native trees releases more carbon

We established 160 experimental plant communities, with different combinations of native and non-native plants. We collected and reared herbivorous insects and created identical mixtures which we added to half of the plots.

We also cultured soil microorganisms to create two different soils that we split across the plant communities. One soil contained microorganisms familiar to the plants and another was unfamiliar.

Herbivorous insects and soil microorganisms feed on live and decaying plant tissue. Their ability to grow depends on the nutritional quality of that food. We found that non-native plants provided a better food source for herbivores compared with native plants – and that resulted in more plant-eating insects in communities dominated by non-native plants.

Similarly, exotic plants also raised the abundance of soil microorganisms involved in the rapid decomposition of plant material. This synergy of multiple organisms and interactions (fast-growing plants with less dense tissues, high herbivore abundance, and increased decomposition by soil microorganisms) means that more of the plant carbon is released back into the atmosphere.

In a practical sense, these soil treatments (soils with microorganisms familiar vs. unfamiliar to the plants) mimic the difference between reforestation (replanting an area) and afforestation (planting trees to create a new forest).

Reforested areas are typically replanted with native species that occurred there before, whereas afforested areas are planted with new species. Our results suggest planting non-native trees into soils with microorganisms they have never encountered (in other words, afforestation with non-native plants) may lead to more rapid release of carbon and undermine the effort to mitigate climate change.

Lauren Waller, Postdoctoral Fellow and Warwick Allen, Postdoctoral fellow, University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Lemurs are the world’s most endangered mammals, but planting trees can help save them

Black-and-white ruffed lemurs are important indicators of rainforest health.
Franck Rabenahy, CC BY-ND

Andrea L. Baden, Hunter College

Madagascar, the world’s fourth-largest island, is a global biodiversity hotspot.
Andrea Baden

The island of Madagascar off the southeastern coast of Africa hosts at least 12,000 plant species and 700 vertebrate species, 80% to 90% of which are found nowhere else on Earth.

Isolated for the last 88 million years and covering an area approximately the size of the northeastern United States, Madagascar is one of the world’s hottest biodiversity hotspots. Its island-wide species diversity is striking, but its tropical forest biodiversity is truly exceptional.

Sadly, human activities are ravaging tropical forests worldwide. Habitat fragmentation, over-harvesting of wood and other forest products, over-hunting, invasive species, pollution and climate change are depleting many of these forests’ native species.

Among these threats, climate change receives special attention because of its global reach. But in my research, I have found that in Madagascar it is not the dominant reason for species decline, although of course it’s an important long-term factor.

As a primatologist and lemur specialist, I study how human pressures affect Madagascar’s highly diverse and endemic signature species. In two recent studies, colleagues and I have found that in particular, the ruffed lemur – an important seed disperser and indicator of rainforest health – is being disproportionately impacted by human activities. Importantly, habitat loss is driving ruffed lemurs’ distributions and genetic health. These findings will be key to helping save them.

Deforestation from slash-and-burn agriculture in the peripheral zones of Ranomafana National Park, Madagascar.
Nina Beeby/Ranomafana Ruffed Lemur Project, CC BY-ND

The forest is disappearing

Madagascar has lost nearly half (44%) of its forests within the last 60 years, largely due to slash-and-burn agriculture – known locally as “tavy” – and charcoal production. Habitat loss and fragmentation runs throughout Madagascar’s history, and the rates of change are staggering.

This destruction threatens Madagascar’s biodiversity and its human population. Nearly 50% of the country’s remaining forest is now located within 300 feet (100 meters) of an unforested area. Deforestation, illegal hunting and collection for the pet trade are pushing many species toward the brink of extinction.

In fact, the International Union for Conservation of Nature estimates that 95% of Madagascar’s lemurs are now threatened, making them the world’s most endangered mammals. Pressure on Madagascar’s biodiversity has significantly increased over the last decade.

A red ruffed lemur, one of two *Varecia* species endemic to Madagascar.
Varecia Garbutt, CC BY-ND

Deforestation threatens ruffed lemur survival

In a newly published study, climate scientist Toni Lyn Morelli, species distribution expert Adam Smith and I worked with 19 other researchers to study how deforestation and climate change will affect two critically endangered ruffed lemur species over the next century. Using combinations of different deforestation and climate change scenarios, we estimate that suitable rainforest habitat could be reduced by as much as 93%.

If left unchecked, deforestation alone could effectively eliminate ruffed lemurs’ entire eastern rainforest habitat and with it, the animals themselves. In sum, for these lemurs the effects of forest loss will outpace climate change.

But we also found that if current protected areas lose no more forest, climate change and deforestation outside of parks will reduce suitable habitat by only 62%. This means that maintaining and enhancing the integrity of protected areas will be essential for saving Madagascar’s rainforest habitats.

Warm colors indicate areas where lemurs can move about readily, which promotes genetic diversity; cool colors indicate areas where they are more constrained and less able to mate with members of other population groups.
Baden et al. (2019), Nature Scientific Reports, CC BY-ND

In a study published in November 2019, my colleagues and I showed that ruffed lemurs depend on habitat cover to survive. We investigated natural and human-caused impediments that prevent the lemurs from spreading across their range, and tracked the movement of their genes as they ranged between habitats and reproduced. This movement, known as gene flow, is important for maintaining genetic variability within populations, allowing lemurs to adapt to their ever-changing environments.

Based on this analysis, we parsed out which landscape variables – including rivers, elevation, roads, habitat quality and human population density – best explained gene flow in ruffed lemurs. We found that human activity was the best predictor of ruffed lemurs’ population structure and gene flow. Deforestation alongside human communities was the most significant barrier.

Taken together, these and other lines of evidence show that deforestation poses an imminent threat to conservation on Madagascar. Based on our projections, habitat loss is a more immediate threat to lemurs than climate change, at least in the immediate future.

In 1961 naturalist David Attenborough filmed ruffed lemurs for the BBC.

This matters not only for lemurs, but also for other plants and animals in the areas where lemurs are found. The same is true at the global level: More than one-third (about 36.5%) of Earth’s plant species are exceedingly rare and disproportionately affected by human use of land. Regions where the most rare species live are experiencing higher levels of human impact.

Crisis can drive conservation

Scientists have warned that the fate of Madagascar’s rich natural heritage hangs in the balance. Results from our work suggest that strengthening protected areas and reforestation efforts will help to mitigate this devastation while environmentalists work toward long-term solutions for curbing the runaway greenhouse gas emissions that drive climate change.

A young woman participates in reforestation efforts in Kianjavato, Madagascar.
Brittani Robertson/Madagascar Biodiversity Partnership, CC BY-ND

Already, nonprofits are working hard toward these goals. A partnership between Dr. Edward E. Louis Jr., founder of Madagascar Biodiversity Partnership and director of Conservation Genetics at Omaha’s Henry Doorly Zoo, and the Arbor Day Foundation’s Plant Madagascar project has replanted nearly 3 million trees throughout Kianjavato, one region identified by our study. Members of Centre ValBio’s reforestation team – a nonprofit based just outside of Ranomafana National Park that facilitates our ruffed lemur research – are following suit.

At an international conference in Nairobi earlier this year, Madagascar’s president, Andry Rajoelina, promised to reforest 40,000 hectares (99,000 acres) every year for the next five years – the equivalent of 75,000 football fields. This commitment, while encouraging, unfortunately lacks a coherent implementation plan.

Our projections highlight areas of habitat persistence, as well as areas where ruffed lemurs could experience near-complete habitat loss or genetic isolation in the not-so-distant future. Lemurs are an effective indicator of total non-primate community richness in Madagascar, which is another way of saying that protecting lemurs will protect biodiversity. Our results can help pinpoint where to start.

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Andrea L. Baden, Assistant Professor of Anthropology, Hunter College

This article is republished from The Conversation under a Creative Commons license. Read the original article.

When tree planting actually damages ecosystems

Giraffes prefer the open space and scattered trees of the African savanna.
Volodymyr Burdiak/Shutterstock

Kate Parr, University of Liverpool and Caroline Lehmann, University of Edinburgh

Tree planting has been widely promoted as a solution to climate change, because plants absorb the climate-warming gases from Earth’s atmosphere as they grow. World leaders have already committed to restoring 350m hectares of forest by 2030 and a recent report suggested that reforesting a billion hectares of land could store a massive 205 gigatonnes of carbon – two thirds of all the carbon released into the atmosphere since the Industrial Revolution.

Many of those trees could be planted in tropical grassy biomes according to the report. These are the savannas and grasslands that cover large swathes of the globe and have a grassy ground layer and variable tree cover. Like forests, these ecosystems play a major role in the global carbon balance. Studies have estimated that grasslands store up to 30% of the world’s carbon that’s tied up in soil. Covering 20% of Earth’s land surface, they contain huge reserves of biodiversity, comparable in areas to tropical forest. These are the landscapes with lions, elephants and vast herds of wildebeest.

Gorongosa, Mozambique. The habitat here is open, well-lit and with few trees.
Caroline Lehmann, Author provided

Savannas and grasslands are home to nearly one billion people, many of whom raise livestock and grow crops. Tropical grassy biomes were the cradle of humankind – where modern humans first evolved – and they are where important food crops such as millet and sorghum originated, which millions eat today. And, yet among the usual threats of climate change and wildlife habitat loss, these ecosystems face a new threat – tree planting.

It might sound like a good idea, but planting trees here would be damaging. Unlike forests, ecosystems in the tropics that are dominated by grass can be degraded not only by losing trees, but by gaining them too.

Where more trees isn’t the answer

Increasing the tree cover in savanna and grassland can mean plant and animal species which prefer open, well-lit environments are pushed out. Studies from South Africa, Australia and Brazil indicate that unique biodiversity is lost as tree cover increases.

This is because adding trees can alter how these grassy ecosystems function. More trees means fires are less likely, but regular fire removes vegetation that shades ground layer plants. Not only do herbivores like zebra and antelope that feed on grass have less to eat, but more trees may also increase their risk of being eaten as predators have more cover.

A mosaic of grassland and forest in Gabon.
Kate Parr, Author provided

More trees can also reduce the amount of water in streams and rivers. As a result of humans suppressing wildfires in the Brazilian savannas, tree cover increased and the amount of rain reaching the ground shrank. One study found that in grasslands, shrublands and cropland worldwide where forests were created, streams shrank by 52% and 13% of all streams dried up completely for at least a year.

Grassy ecosystems in the tropics provide surface water for people to drink and grazing land for their livestock, not to mention fuel, food, building materials and medicinal plants. Tree planting here could harm the livelihoods of millions.

Losing ancient grassy ecosystems to forests won’t necessarily be a net benefit to the climate either. Landscapes covered by forest tend to be darker in colour than savanna and grassland, which might mean they also absorb more heat. As drought and wildfires become more frequent, grasslands may be a more reliable carbon sink than forests.

Redefine forests

How have we reached the point where the unique tropical savannas and grasslands of the world are viewed as suitable for wholesale “restoration” as forests?

At the root of the problem is that these grassy ecosystems are fundamentally misunderstood. The Food and Agricultural Organisation of the UN defines any area that’s half a hectare in size with more than 10% tree cover as forest. This assumes that landscapes like an African savanna are degraded because they have fewer trees and so need to be reforested. The grassy ground layer houses a unique range of species, but the assumption that forests are more important threatens grassy ecosystems across the tropics and beyond, including in Madagascar, India and Brazil.

A flowering aloe in Madagascan grassland.
Caroline Lehmann, Author provided

“Forest” should be redefined to ensure savannas and grasslands are recognised as important systems in their own right, with their own irreplaceable benefits to people and other species. It’s essential people know what degradation looks like in open, sunlit ecosystems with fewer trees, so as to restore ecosystems that are actually degraded with more sensitivity.

Calls for global tree planting programmes to cool the climate need to think carefully about the real implications for all of Earth’s ecosystems. The right trees need to be planted in the right places. Otherwise, we risk a situation where we miss the savanna for the trees, and these ancient grassy ecosystems are lost forever.

Kate Parr, Professor of Tropical Ecology, University of Liverpool and Caroline Lehmann, Senior Lecturer in Biogeography, University of Edinburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Exaggerating how much CO₂ can be absorbed by tree planting risks deterring crucial climate action

A long way to go…
Amenic181/Shutterstock

Duncan McLaren, Lancaster University

Planting almost a billion hectares of trees worldwide is the “biggest and cheapest tool” for tackling climate change, according to a new study. The researchers claimed that reforestation could remove 205 gigatonnes of carbon from the atmosphere – equivalent to about 20 years’ worth of the world’s current emissions. This has criticised as an exaggeration. It could actually be dangerous.

While the paper itself included no costings, the researchers suggested a best-case estimate of just US$300 billion to plant trees on 0.9 billion hectares. That’s just 40 US cents per tonne of carbon dioxide (CO₂) removed. More detailed studies on the costs of carbon removal through reforestation put the figure closer to US$20-50 per tonne – and even this may be optimistic at such large scales.

Our research suggests that the promises implied in such studies could actually set back meaningful action on climate change. This is because of what we call “mitigation deterrence” – promises of cheap and easy CO₂ removal in future make it less likely that time and money will be invested in reducing emissions now.

Why would anyone expect governments or the finance sector to invest in renewable energy, or mass transit like high-speed rail, at costs of tens or hundreds of dollars a tonne if they – and shareholders and voters – are told that huge amounts of CO₂ can be absorbed from the atmosphere for a few dollars a tonne by planting trees?

Why should anyone expect energy companies and airlines to reduce their emissions if they anticipate being able to pay to plant trees to offset everything they emit, for the paltry price of less than 50 cents a tonne. If studies like this suggest removing carbon is cheap and easy, the price of emitting carbon for businesses – in emissions trading schemes – will remain very low, rather than rising to the levels needed to trigger more challenging, yet urgently needed, forms of emission reduction.

Tree planting is cheaper but less effective at reducing emissions than building zero-carbon infrastructure like electric high-speed rail.
Pedrosala/Shutterstock

A false carbon economy

The promises of cheap and powerful tech fixes help to sideline thorny issues of politics, economics and culture. But when promises that look great in models and spreadsheets meet the real world, failure is often more likely. This has been seen before in the expectations around carbon capture and storage.

Despite promises of its future potential in the early 2000s, commercial development of the technology has scarcely progressed in the last decade. That’s despite many modelled pathways for limiting global warming still assuming – increasingly optimistically – that it will be deployed at a large scale in coming decades.

This model of tackling climate change goes hand in hand with another tool – pricing carbon emissions. This potentially allows companies to go on emitting by paying someone else to cut emissions or remove CO₂ elsewhere – an approach called climate offsetting. But offsetting makes exaggerated promises of carbon removal even more risky.

Tree planting financed through offset markets would guarantee the polluter could continue emitting carbon, but the market couldn’t guarantee removals to match those emissions. Trees might be planted and subsequently lost to wildfire or logging, or never planted at all.

Trusting in trees to remove carbon in future is particularly dangerous because trees are slow to grow and how much carbon they absorb is hard to measure. They’re also less likely to be able to do this as the climate warms. In many regions of the world but particularly in the tropics, growth rates are predicted to fall as the climate warms and devastating wildfires become more frequent.

Relying on trees to absorb CO₂ from the atmosphere in the future also appears misleadingly cheap because of the effects of economic discounting. Economists discount the current value of costs or benefits more deeply, the further in the future they occur. Models which determine the cheapest mix of policies available all use some form of discounting.

When researchers add carbon removal options like tree planting to these models, they tend to generate pathways for slowing temperature rise which reduce the role of short term action and replace it with imaginary removals late in the century.

This is because discounting over 30 to 60 years makes the removal options look incredibly cheap in today’s prices. Priming models to focus on minimising cost causes them to maximise the use of discounted future removals and reduce the use of more expensive near term emissions reduction.

I am not arguing against reforestation, nor for a purely technological response to climate change. Trees can help for many reasons – reducing flooding, shading and cooling communities, and providing habitat for biodiversity. Incentives for reforestation are important, and so are incentives for removing carbon. But we shouldn’t make trees or technology carry the whole burden of tackling climate change. That demands moving beyond technical questions, to deliver immediate political action to cut emissions, and to begin to transform economies and societies.

This article was amended on July 13 2019 to clarify the proposed costs of carbon removal by reforestation.

Duncan McLaren, Professor in Practice, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Lemurs are the world’s most endangered mammals, but planting trees can help save them

Andrea L. Baden, Hunter College

The island of Madagascar off the southeastern coast of Africa hosts at least 12,000 plant species and 700 vertebrate species, 80% to 90% of which are found nowhere else on Earth.

The forest is disappearing

Deforestation threatens ruffed lemur survival

In 1961 naturalist David Attenborough filmed ruffed lemurs for the BBC.

Crisis can drive conservation

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Andrea L. Baden, Assistant Professor of Anthropology, Hunter College

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Greenwashing: corporate tree planting generates goodwill but may sometimes harm the planet

File 20180924 85773 b469v3.jpg?ixlib=rb 1.1 — Missing the wood for the trees.
iDraw/Shutterstock

Benjamin Neimark, Lancaster University

Trees do a lot more for us than you probably think. Their roots prevent soil from eroding, their canopies provide shade and their leaves decompose into nutrients for crops, which feed livestock. Trees provide homes for a diverse range of wildlife and tree crops, such as coffee, rubber, and hardwoods, support countless livelihoods and entire economies. Trees also mark boundaries and hold immense spiritual, cultural and social value for smallholder communities around the world.

In the 1980s, charities proposed planting more trees to halt “desertification” in the Sahara Desert. This involved “afforestation” – planting trees where they had not grown for a while and “reforestation” – replacing recently lost tree cover.

Today the idea is growing strong, and an array of private companies from adult website Pornhub (yes, Pornhub) to clothing brand Ten Tree are using trees as a marketing tool.

Saving face or saving forests?

Businesses can offset their environmental impact by planting trees or supporting other forms of habitat restoration, so as to “pay off” the damage they cause locally. As climate change escalates, trees are in vogue for their potential to soak up the carbon dioxide we keep putting in the atmosphere.

The United Nations (UN) has even adopted a scheme for offering local communities and governments some sort of financial payout for saving trees from deforestation. This “economy of repair” has been adopted by some of the largest companies in their commitments to corporate social responsibility. One such programme is the Green Belt Movement – a Kenyan conservation NGO started by the late professor and Nobel Prize recipient Wangari Maathai.

Tree planting around the Sahara Desert has overwhelmingly relied on local efforts rather than businesses.
Niels Polderman/Shutterstock

Maathai’s original mission was to empower local people, particularly women, to overcome inequality through leading forest restoration and resisting the expanding Sahara Desert. Despite the involvement of charities and businesses, research has suggested that in programmes like these, it is farmers and local people, not companies, which make the biggest contributions to planting new trees. Since local people also inherit responsibility for them, it’s important that projects devised by outside parties are planned and executed wisely, and in the community’s interest.

While some may argue that tree planting is a win-win for the environment whoever does it, offsetting is just another way of corporate greenwashing. Environmental damage in one place cannot somehow be fixed by repairing habitats elsewhere, sometimes on the other side of the world.

Here are some of the ways in which indiscriminate tree planting can cause more harm than good.

Plantations are not forests

Diverse forests are often cleared for agricultural production or industrial use, and replaced by uniform stands of the same species selected because of their ability to grow fast.

Tropical forests in some cases take up to 65 years to regrow and their diversity cannot be replicated by a monoculture of reforested plots.

Ecologically illiterate

Reforestation and afforestation schemes must decide which species are appropriate to plant – native or exotic, multi-purpose or fast growing, naturally regenerating forests or managed plantations. Sometimes the wrong species are selected and Eucalyptus (Eucalyptus globulus) is one such poor choice.

Eucalyptus is usually chosen because it is fast growing and economically valuable. Yet, it is exotic to many places it is now planted and requires lots of water, which drains the water table and competes with native crops.

In Europe, replacing broad-leafed native oak trees with faster growing conifers has meant that forest cover on the continent is 10% greater than it was before the industrial revolution. However, the new trees are not as good at trapping carbon but do trap heat more efficiently, contributing to global warming. Clearly, tree planting without due caution can do more harm than good.

Trees need care – lots of it

Tree species take a long time to grow and need continual care. However, tree planting schemes usually “plant and go” –- meaning they do not put resources into managing the trees after they are placed into the ground. Young trees are particularly vulnerable to disease and competition for light and nutrients and if not cared for, will eventually die.

Newly planted tree saplings may need three to five years of frequent watering to survive.
A3pfamily/Shutterstock

Trees are political

Trees planted by states or private donors may choose sites without consulting local communities, ignoring any of their customary land rights and management regimes. This locally-owned land may be in fallow or have different economic, cultural or spiritual uses.

Blundering into planting in these places may exacerbate tensions over land tenure, spreading disinterest in tree care and stewardship. Dispossessed locals may move to existing forests and clear land for food production. Tenure rights over trees are also not always owned by whole households either, but divided between gender. Planting trees and asking questions later may sow tensions over land ownership for long after the project departs.

It’s no surprise that trees are on the green economy agenda, but this does not necessarily mean that planting them is “green” or helpful for social harmony. Allowing trees to regrow naturally is not always effective either, as trees are unlikely to survive on their own. Community involvement is therefore crucial.

This means real consultation over site and species selection, property rights over the trees, their products, and the land they grow in and who takes on the labour to keep the trees alive after they are planted. If companies are serious about planting trees then they need to care about the communities that live with them and not just their own reputations.

Benjamin Neimark, Senior Lecturer, Lancaster Environment Centre, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Stopping land clearing and replanting trees could help keep Australia cool in a warmer future

Clive McAlpine, The University of Queensland; Jozef Syktus, The University of Queensland, and Leonie Seabrook, The University of Queensland

Land clearing is on the rise in Queensland and New South Wales, with land clearing laws being fiercely debated.

In Queensland in 2013–14, 278,000 hectares of native vegetation were cleared (1.2 times the size of the Australian Capital Territory). A further 296,000ha were cleared in 2014–15. These are the highest rates of deforestation in the developed world.

Land clearing on this scale is bad for a whole host of reasons. But our research shows that it is also likely to make parts of Australia warmer and drier, adding to the effects of climate change.

How do trees change the climate?

Land clearing releases greenhouse gases into the atmosphere, but the effect of land clearing on climate goes well beyond carbon emissions. It causes warming locally, regionally and even globally, and it changes rainfall by altering the circulation of heat and moisture.

Trees evaporate more water than any other vegetation type – up to 10 times more than crops and pastures. This is because trees have root systems that can access moisture deep within the soil. Crops and pastures have 70% of their roots in the top 30cm of the soil, while trees and other woody plants have 43% of their roots in the deeper part of the soil.

The increased evaporation and rough surface of trees creates moist, turbulent layers in the lower atmosphere. This reduces temperatures and contributes to cloud formation and increased rainfall. The increased rainfall then provides more moisture to soils and vegetation.

The clearing of deep-rooted native vegetation for shallow-rooted crops and pastures diminishes this process, resulting in a warmer and drier climate.

We can see this process at work along the “bunny fence” in southwest Western Australia, where there is a moister atmosphere and more clouds over native vegetation compared with nearby farming areas during summer.

Studies in Amazonia also indicate that as deforestation expands rainfall declines. A tipping point may be reached when deforestation reaches 30-50%, after which rainfall is substantially reduced. Complete deforestation results in the greatest decline in rainfall.

More trees, cooler moister climate

We wanted to know how land clearing could affect Australia’s climate in the future. We did this by modelling two scenarios for different amounts of land clearing, using models developed by CSIRO.

In the first scenario, crops and pasture expand in the semi-arid regions of eastern and southwest Australia. The second scenario limits crops and pastures to highly productive lands, and partially restores less productive lands to savanna woodlands.

We found that restoring trees to parts of Australia would reduce surface temperatures by up to 1.6℃, especially in western Queensland and NSW.

We also found that more trees reduced the overall climate-induced warming from 4.1℃ to 3.2℃ between 2050 and 2100.

Replanting trees could increase summer rainfall by 10% overall and by up to 15.2% in the southwest. We found soil moisture would increase by around 20% in replanted regions.

Our study doesn’t mean replanting all farmed land with trees, just areas that are less productive and less cost-effective to farm intensively. In our scenario, the areas that are restored in western Queensland and NSW would need a tree density of around 40%, which would allow a grassy understorey to be maintained. This would allow some production to continue such as cattle grazing at lower numbers or carbon farming.

Political and social challenges

Limiting land clearing represents a major challenge for Australia’s policymakers and farming communities.

The growing pressure to clear reflects a narrow economic focus on achieving short- to medium-term returns by expanding agriculture to meet the growing global demand for food and fibre.

However, temperatures are already increasing and rainfall is decreasing over large areas of eastern and southwest Australia. Tree clearing coupled with climate change will make growing crops and raising livestock even harder.

Balancing farming with managing climate change would give land owners on marginal land new options for income generation, while the most efficient agricultural land would remain in production. This would need a combination of regulation and long-term financial incentives.

The climate benefits of limiting land clearing must play a bigger part in land management as Australia’s climate becomes hotter and drier. Remnant vegetation needs to be conserved and extensive areas of regrowth must be allowed to regenerate. And where regeneration is not possible, we’ll have to plant large numbers of trees.

Clive McAlpine, Professor, The University of Queensland; Jozef Syktus, Principal Research Fellow, Global Change Institute, The University of Queensland, and Leonie Seabrook, Landscape Ecologist, The University of Queensland

This article was originally published on The Conversation. Read the original article.

Stop the miners: you can help Australia’s birds by planting native gardens

Kathryn Teare Ada Lambert, University of New England

Some Australian birds are pushing out other species, and even damaging trees. Noisy and bell miners are two of Australia’s most aggressive bird species. Found throughout eastern Australia, in recent years their numbers have increased at the expense of our smaller birds.

Both species are spreading to new areas, largely due to human destruction of habitat. Noisy miners are able to invade areas where habitat has been modified, particularly gardens.

Bell miners, meanwhile, can invade areas that have invasions of weeds in the understorey such as blackberry and lantana that they use for nesting.

The good news is we can help stop the spread of these birds, by putting native plants in our gardens.

Masked mobster: noisy miners are increasing in number and spreading at the expense of smaller birds.
Kathryn Lambert, Author provided

Good birds gone bad

Both species of these miners (genus Manorina) have been found to reduce bird diversity through their aggressive behaviour, and have been associated with eucalypt dieback.

Human disturbance has been linked to increasing numbers of noisy miners. One study in the box-ironbark forests of southeast Australia, found that noisy miners an move into areas of smaller fragments and unhealthy trees.

They then chase away other birds, reducing the number of species and potentially having knock-on effects on ecosystems. The problem is so serious that noisy miners are listed as a national threatening process.

More research is needed to find out why bell miners are becoming more common. But our research has found that bell miners show similar behaviour to noisy miners. They have a distinctive call that travels for tens of metres through the forest.

Bell miners cause Bell Miner Associated Dieback in trees. It is thought that their feeding and breeding behaviours lead to the death of eucalypts on the east coast of Australia. They also take over habitat that would be used by other birds.

Bell miners are known for their loud calls.
Sascha Wenninger/Flickr, CC BY-SA

Are the birds to blame?

Where miners are normally found in lower numbers, disturbances by people can tip the balance in their favour. This includes increasing noise levels, removing corridors of connecting native vegetation, creating gardens with exotic plants, building cities, houses, parks, logging and introducing invasive species that create thick understories.

These disturbances increase the habitat available for these two species, allowing them to increase in number and drive out the smaller birds that compete for their food sources.

Noisy miners particularly favour open areas that don’t have thickets of shrubs of smaller trees underneath the canopy. Conversely, bell miners prefer thick understoreys, particularly those create by introduced weeds such as lantana.

So if we are causing these birds to increase in number, how can we reduce their numbers and re-create the original habitat where all species could co-exist?

Build a bird-friendly garden

You need to create a multi-layered habitat of ground covers, small and medium shrubs, and trees that provide food and shelter locations all year for a variety of species.

These plant species need to have diverse structures, and should be close together to form dense, protective thickets, including climbers within medium-to-tall shrubs and trees, nectar-bearing and seed-bearing plants. Mulch can also encourage insect life for insectivorous birds.

Plants should also be local species that grow naturally in the area and are suited to the climate. Native birds that live in the area will then visit your garden as another food source in their territory.

A bird-friendly garden.
Karthryn Lambert, Author provided

Reducing weeds in your garden and neighbouring bushland (many weeds are derived from garden plants) can help native species. General natives can also be planted if you can’t find local natives in your local nursery.

Even in gardens where noisy miners dominate, smaller birds can survive in a dense understorey.

Meanwhile, a thin midstorey with fewer leaves may help to reduce bell miner abundance, as suggested by our recent study near Kyogle, New South Wales.

You should also consider the timing of flower and fruit production, to ensure that there is always food available for birds. You should also remove fruiting plants such as cotoneaster and blackberry that attract predators such as currawongs, to help reduce predation on smaller bird species.

Using chemical-free weed and pest control and mulching garden waste can also increase the food available for birds.

Lawns can also be replaced with native grasses that produce seed to attract finches and other seed-eaters such as crimson rosellas. Birds also need fresh water, which you can provide with a pond or bird bath. This should be placed within vegetation to ensure birds feel safe from predators.

Why are native gardens important?

Local biodiversity can be maintained by native gardens, ensuring long-term ecological sustainability. Small birds and other wildlife benefit from planting native species.

Many species are negatively affected by the current structure of gardens such as lawns, few scattered trees and the placement of concrete and houses without any access to nesting habitat.

Gardening in Australia needs to be changed to favour more native species and provide structure on a landscape scale that includes a variety of gardens.

Kathryn Teare Ada Lambert, Research Associate, University of New England

This article was originally published on The Conversation. Read the original article.

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Redefine forests

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A false carbon economy

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The forest is disappearing

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Crisis can drive conservation

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Saving face or saving forests?

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How do trees change the climate?

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Political and social challenges

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Good birds gone bad

Are the birds to blame?

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