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.

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Statistic of the decade: The massive deforestation of the Amazon

Aerial view of deforested area of the Amazon rainforest.
PARALAXIS/Shutterstock.com

Liberty Vittert, Washington University in St Louis

This year, I was on the judging panel for the Royal Statistical Society’s International Statistic of the Decade.

Much like Oxford English Dictionary’s “Word of the Year” competition, the international statistic is meant to capture the zeitgeist of this decade. The judging panel accepted nominations from the statistical community and the public at large for a statistic that shines a light on the decade’s most pressing issues.

On Dec. 23, we announced the winner: the 8.4 million soccer fields of land deforested in the Amazon over the past decade. That’s 24,000 square miles, or about 10.3 million American football fields.

This statistic, while giving only a snapshot of the issue, provides insight into the dramatic change to this landscape over the last 10 years. Since 2010, mile upon mile of rainforest has been replaced with a wide range of commercial developments, including cattle ranching, logging and the palm oil industry.

This calculation by the committee is based on deforestation monitoring results from Brazil’s National Institute for Space Research, as well as FIFA’s regulations on soccer pitch dimensions.

Calculating the cost

There are a number of reasons why this deforestation matters – financial, environmental and social.

First of all, 20 million to 30 million people live in the Amazon rainforest and depend on it for survival. It’s also the home to thousands of species of plants and animals, many at risk of extinction.

Second, one-fifth of the world’s fresh water is in the Amazon Basin, supplying water to the world by releasing water vapor into the atmosphere that can travel thousands of miles. But unprecedented droughts have plagued Brazil this decade, attributed to the deforestation of the Amazon.

During the droughts, in Sao Paulo state, some farmers say they lost over one-third of their crops due to the water shortage. The government promised the coffee industry almost US$300 million to help with their losses.

Finally, the Amazon rainforest is responsible for storing over 180 billion tons of carbon alone. When trees are cleared or burned, that carbon is released back into the atmosphere. Studies show that the social cost of carbon emissions is about $417 per ton.

Finally, as a November 2018 study shows, the Amazon could generate over $8 billion each year if just left alone, from sustainable industries including nut farming and rubber, as well as the environmental effects.

Financial gain?

Some might argue that there has been a financial gain from deforestation and that it really isn’t a bad thing. Brazil’s president, Jair Bolsonaro, went so far as to say that saving the Amazon is an impediment to economic growth and that “where there is indigenous land, there is wealth underneath it.”

In an effort to be just as thoughtful in that sense, let’s take a look. Assume each acre of rainforest converted into farmland is worth about $1,000, which is about what U.S. farmers have paid to buy productive farmland in Brazil. Then, over the past decade, that farmland amounts to about $1 billion.

The deforested land mainly contributes to cattle raising for slaughter and sale. There are a little over 200 million cattle in Brazil. Assuming the two cows per acre, the extra land means a gain of about $20 billion for Brazil.

Chump change compared to the economic loss from deforestation. The farmers, commercial interest groups and others looking for cheap land all have a clear vested interest in deforestation going ahead, but any possible short-term gain is clearly outweighed by long-term loss.

Rebounding

Right now, every minute, over three football fields of Amazon rainforest are being lost.

What if someone wanted to replant the lost rainforest? Many charity organizations are raising money to do just that.

At the cost of over $2,000 per acre – and that is the cheapest I could find – it isn’t cheap, totaling over $30 billion to replace what the Amazon lost this decade.

Still, the studies that I’ve seen and my calculations suggest that trillions have been lost due to deforestation over the past decade alone.

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Liberty Vittert, Professor of the Practice of Data Science, Washington University in St Louis

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

Where does beach sand come from?

This started as a mountain range.
Bas Meelker/Shutterstock.com

David R. Montgomery, University of Washington

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.

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Where does beach sand come from? – Sly M., age 6, Cambridge, Massachusetts

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There’s more to beach sand than meets the eye. It has stories to tell about the land, and an epic journey to the sea. That’s because mountains end their lives as sand on beaches.

Over time, mountains erode. The mud, sand, gravel, cobbles and boulders they shed are washed into streams, which come together to form rivers. As they flow down to the sea, all this sediment is ground up and worn down in nature’s version of a rock tumbler.

Big rocks break down into smaller pieces, so most of what reaches the sea is mud. These silt and clay particles are too small to perceive with the naked eye. But you can see individual grains of sand, which are just bigger bits of rock.

Next time you’re at the beach, pick up a handful of sand and look closely at it. Are all the grains the same color, or a rainbow assortment? Are they jagged and angular, or smooth and round?

Some beaches in Hawaii have black sand because the islands were formed by erupting volcanoes. Many volcanic minerals are dark colored.
dronepicr/Wikipedia, CC BY

Different colors of sand come from different minerals, like khaki feldspar, smoky white quartz, green olivine or black basalt. The mix of colors in beach sand tells you what kinds of rocks produced it.

The shape of sand grains also provides clues about where they come from. Angular grains of the same type of sand have not traveled as far as smooth round grains, which have been more worn down. And weak rocks break down to mud faster than hard rocks, so sand tends to be made of the harder types that break down slowly.

About a tenth of the supply of sediment that reaches the sea is sand. These particles are between about half a millimeter and 2 millimeters in size – roughly as thick as a penny. These particles are large enough that they don’t flow right out to the deep sea.

But the beach is just a temporary stop for sand. Big waves pull it offshore, and smaller waves push it along the coast. So keeping a beach nourished with sand is essential for keeping it sandy.

Many beach towns spend millions of dollars to rebuild eroded beaches with new sand.

Yet today many beaches are starving. Many dams trap the sand that flows down rivers, piling it up in reservoirs. All in all, human activity has cut off about half the sand that would otherwise end up on the world’s beaches.

But humans haven’t turned the waves off, so as beach sand washes away and isn’t replenished, the shoreline erodes. That means that many beaches around the world are shrinking, slowly but surely.

So next time you dig your toes into beach sand think about the epic journey it took to arrive beneath your feet. Take a moment to think about where the sand came from and where it’s going.

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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.

David R. Montgomery, Professor of Earth and Space Sciences, University of Washington

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