African Desert is Home to Abundant Forest Growth

Researchers have found an unknown wealth of trees in an African desert zone supposedly too arid for green growth.

Rural Burkina Faso: Part of the Sahel, but with plenty of trees. Image: By Adam Jones, Ph.D., via Wikimedia Commons
Burkina Faso: Part of the Sahel, but with plenty of trees. Image: By Adam Jones, Ph.D., via Wikimedia Commons.

By Tim Radford, Climate News Network (CC BY-ND 4.0)

With help from high resolution satellite imagery and some advanced artificial intelligence techniques, European scientists have been counting the trees in a parched African desert.

They pored over 1.3 million square kilometres of the waterless western Sahara and the arid lands of the Sahel to the south, to identify what is in effect an unknown forest. This region − a stretch of dunes and dryland larger than Angola, or Peru, or Niger − proved to be home to 1.8 billion trees and shrubs with crowns larger than three square metres.

“We were very surprised to see that quite a few trees actually grow in the Sahara Desert because up till now, most people thought that virtually none existed. We counted hundreds of millions of trees in the desert alone,” said Martin Brandt, a geographer at the University of Copenhagen in Denmark, who led the research.

He and colleagues from Germany, France, Senegal, Belgium and Nasa in the US report in the journal Nature that they used an artificial intelligence technique called “deep learning” and satellite imagery so advanced that − from space − a camera could resolve an object half a metre or more in diameter, to see if they could answer unresolved questions about all those trees beyond the world’s forests.

Trees outside of forested areas are not usually included in climate models, and we know very little about their carbon stocks. They are  an unknown component in the global carbon cycle”.

—Martin Brandt, lead researcher, University of Copenhagen

Trees matter, wherever they are. In cities, they enhance urban life and sustain property values. In forests, they conserve and recycle water, shelter millions of animals and smaller plants, and absorb atmospheric carbon. In grasslands they conserve soils, offer habitat for species and provide subsistence fuel, food and fodder for humans and animals.
But trees beyond the forests are an unknown factor when it comes to the puzzle of the global carbon budget and the great challenge of containing runaway climate change.

“Trees outside of forested areas are not usually included in climate models, and we know very little about their carbon stocks,” Dr Brandt said. “They are basically a white spot on maps and an unknown component in the global carbon cycle.”

The total identified in the target zone of the Sahara and the Sahel is almost certainly an under-estimate: the technology did not and could not pinpoint trees with a crown or shade area smaller than 3 square metres.

The study adds to the chronicle of surprises delivered by tree and forest research. In the last few years scientists have essayed a global census of woody growths wider than 5cms at breast height − that’s the botanist’s definition of a tree − and arrived at a total of more than 3 trillion.

New map possible

They have also counted the different kinds of tree: more than 60,000 species. They have already made attempts to measure the extent of tree cover in dryland and savannah regions and identified a kind of hidden forest.

They have calculated that a determined global tree planting campaign could absorb enough carbon to make a formidable difference to the challenge of global heating, and they have confirmed that conserved natural forests are, even on the simple basis of human economics, a bargain: forests are worth more to the world when they flourish than when they are cleared.

The new approach − the match of artificial intelligence with high resolution imagery − could one day help identify not just trees, but different tree species. It could, researchers hope, eventually even provide a reliable count of trees in a forest, although where canopies overlap it will always be difficult to number the trunks that support them. It offers the world’s forest scientists a new starting point for a map of all the planet’s trees.

“Doing so wouldn’t have been possible without this technology,” Dr Brandt said. “Indeed, I think it marks the beginning of a new scientific era.” 


Original publication: Climate News Network — LONDON, 27 October, 2020

Tracking 3 Decades of Dramatic Glacial Lake Growth

In the largest-ever study of glacial lakes, researchers using a 30-year satellite data record have found that the volume of these lakes worldwide has increased by about 50% since 1990.
Credits: NASA

In the largest-ever study of glacial lakes, researchers using 30 years of NASA satellite data have found that the volume of these lakes worldwide has increased by about 50% since 1990 as glaciers melt and retreat due to climate change.

The findings, published in the journal Nature Climate Change, will aid researchers assessing the potential hazards to communities downstream of these often unstable lakes and help improve the accuracy of sea-level rise estimates by advancing our understanding of how glacial meltwater is transported to the oceans.

Glaciers are retreating on a near-global scale and this study provides scientists with a clearer picture of how much of this water has been stored in lakes.

“We have known that not all meltwater is making it into the oceans immediately,” said lead author Dan Shugar of the University of Calgary in Canada. “But until now there were no data to estimate how much was being stored in lakes or groundwater.” The study estimates current glacial lake volumes total about 37.4 cubic miles (156 cubic kilometers) of water, the equivalent of about one-third the volume of Lake Erie.

Shugar and his collaborators from governments and universities in Canada, the United States, and the United Kingdom, working under a grant from NASA’s High Mountain Asia Program, initially planned to use satellite imaging and other remote-sensing data to study two dozen glacial lakes in High Mountain Asia, the geographic region that includes the Tibetan Plateau and surrounding mountain ranges, including the Himalaya.

“We wrote scripts in Google Earth Engine, an online platform for very large analyses of geospatial data, to look only at High Mountain Asia, and then decided to look at all glacial lakes in the world,” Shugar said. “From there, we were able to build a scaling relationship to estimate the volume of the world’s glacial lakes based on the area of this large population of lakes.”

The team ultimately analyzed more than 250,000 scenes from the Landsat satellite missions, a joint NASA/U.S. Geological Survey program. A decade ago it would not have been possible to process and analyze this volume of data. The team looked at the data in five time-steps beginning with 1990 to examine all the glaciated regions of the world except Antarctica and analyze how glacial lakes changed over that period.

Shugar points out that while water from melting glaciers stored in glacial lakes is a relatively small contributor to overall sea level rise, it can have a major impact on mountain communities downstream of these glacial lakes.

Glacial lakes are not stable like the lakes in which most people are used to swimming or boating because they are often dammed by ice or glacial sediment called a moraine, which is composed of loose rock and debris that is pushed to the front and sides of glaciers. Rather, they can be quite unstable and can burst their banks or dams, causing massive floods downstream. These kinds of floods from glacial lakes, known as glacial lake outburst floods, have been responsible for thousands of deaths over the past century, as well as the destruction of villages, infrastructure, and livestock. A glacial lake outburst flood affected the Hunza Valley in Pakistan in May 2020.

“This is an issue for many parts of the world where people live downstream from these hazardous lakes, mostly in the Andes and in places like Bhutan and Nepal, where these floods can be devastating,” Shugar said. “Fortunately, organizations like the United Nations are facilitating a lot of monitoring and some mitigation work where they’re lowering the lakes to try and decrease the risks.”

In North America, the risks posed by a glacial lake outburst flood are lower.

“We don’t have much in the way of infrastructure or communities that are downstream,” Shugar said. “But we’re not immune to it.”

For more information about NASA’s Earth science programs, visit https://www.nasa.gov/earth.

Environmental Injustice is Rampant Around the World

A study of nearly 700 studies makes it clear: Environmental injustice is rampant around the world

By Rishi Sugla, AAAS Mass Media Fellow, ensia (CC BY-ND 3.0)

August 10, 2020 (originally appeared in ensia on July 30, 2020) — The coronavirus pandemic and resurgence of the Black Lives Matter movement have many environmentalists paying attention to the inextricable links between marginalized peoples and environmental pollution.

The history of disproportionate environmental impacts on Black, Indigenous, and people of color often goes back for centuries. A recent review of 141 Indigenous groups by University of Helsinki conservation researcher Álvaro Fernández-Llamazares and colleagues published in the journal Integrated Environmental Assessment and Management shows how colonialism directly led to the development of environment-polluting infrastructure built without the consent of — and differentially affecting — communities in their territories.

The study, which dug through nearly 700 studies covering six continents to reveal impacts of pollution on the environment, health and culture of Indigenous peoples, points out that this pattern continues today.

Photo by Alev Takil on Unsplash

“The literature reviewed clearly shows that [Indigenous peoples] are among the populations at highest risk of impact by environmental pollution of water, land, and biota through both exposure and vulnerability,” the authors wrote.

The study notes that landfillspipelines, toxic waste storage facilities, sources of radioactive contamination and mines are still being forced upon Indigenous people and directly affect community well-being. In Canada, for example, 20% of drinking water advisories come from Indigenous communities, which make up just 5% of the population. In the western United States, more than 600,000 Native people live within 10 kilometers (6 miles) of an abandoned mine.

Pollution from industrial activities literally flows through Indigenous environments. Contaminants from mines and factories can move into the water, air and soil, where they affect the flora and fauna Indigenous people rely on for traditional hunting, fishing and gathering. Exposure to contaminants has been associated with stark impacts on health.

“Indigenous peoples are particularly vulnerable to the impacts of pollution due to their high and direct dependency on local natural resources, limited access to health care, and relatively low levels of governmental support,” the authors say. Diabetes, hypertension, childhood leukemia, autism, cardiovascular disease, neurological impacts, anemia, cancer, changes in age of menstruation, contaminants in breast milk and anxiety all have been associated with polluting practices on Indigenous territories, the study reports.

Many impacts, however, are not easily measured. The authors write, “While cultural impacts have often been overlooked, the literature suggests that they are substantial in extent and scope.” Environmental degradation, the study notes, has led to the gradual loss of traditional cultural practices that rely on local plants and animals that Indigenous communities hold sacred. Ceremonies that involve drinking water from historical sources can heighten exposure to contaminants. Traditional basket-weaving practices that involve holding reeds in the mouth can become a health risk, for example.

Pollution also affects the spiritual and social health of Indigenous communities. Societal roles are often intimately related to the complex relationships Indigenous peoples have with their environment. Language, culture and community roles surrounding subsistence activities have been abandoned due to contamination and degradation. Spiritual practices involving sacred water sources or sites have similarly been left unviable because of environmental pollutants.

At the same time it documented adverse impact on Indigenous peoples of exposure to contaminants and toxins that they, for the most part, did not create, the study also noted positive impacts Indigenous people have on the environment. Indigenous peoples around the world campaign and resist polluting activities through protests, resistance, demands for policy action and occupation of pollution-producing infrastructure. Many Indigenous communities lead the way at preventing environmental destruction through their direct actions as part of networks of scientists, activists and others, tapping into legal systems when possible. While often framed in public discourse simply as struggles against pollution, the study notes that these actions are directly related to issues of Indigenous sovereignty, justice and land rights.

The study also underscores how traditional management systems help prevent pollution. Indigenous spirituality and social structures tied to the environment protect, remediate and restore sacred sites and community areas. In some cases, these practices have been shown to even support recycling of nutrients in local ecosystems, and Indigenous water cultures have been key to preventing pollution in freshwater environments.

The study concludes that Indigenous people, like many marginalized or oppressed communities, are on the receiving end of disproportionate impacts of environmental pollution. At the same time, these communities are not just victims of pollution. They have long led resistance against pollution-generating industries and activities and worked to protect biodiversity around the world. To reduce the toll of pollution and to maximize the benefits of their environment-protecting actions, the researchers recommend bringing Indigenous people and their perspectives front and center in environmental action.

“Greater engagement of IPs on environmental governance can help to incorporate IPs’ social, spiritual, and customary values in environmental quality and ecosystem health,” they write. “We argue that IPs should be part of any conversation on policy options to reduce risks of pollution to human well‐being, ecosystem services, and biodiversity.”