The surprising ecology of dust (2)
Scientists are unraveling the links between wild weather and climate change.
On the other side of the world, weather patterns in some regions have shifted in a different way. Rainfall in the Sahara has increased because of warmer ocean temperatures, which has meant less dust blowing westward across the Atlantic Ocean. Dust storms have also declined in the deserts of China and South America and are projected to be lower in the Great Plains of the U.S. — all because of an increase in precipitation that stimulates plant growth, which caps the soil.
Dust brings fertility
Peripatetic dust is an ancient and vital geological phenomenon because dust carries nutrients that regulate the distribution of life across the planet. A recent study found that dust from the Gobi Desert — one of the world’s two major sources of dust, along with the Sahara — has long ridden the jet stream and settled in the Sierras in California, where it provides an essential source of life-giving phosphorous for the giant sequoias and other trees in that phosphorous-limited ecosystem. The study found that dust provides even more phosphorous than the other major source — the weathering of bedrock in the mountains.
“Dust is a connector of ecosystems around the world,” said Emma Aronson (plant pathologist and microbiologist at the University of California at Riverside and a co-author of the study).
A massive dust storm in Australia in 2009, known as the Red Dawn, as seen from the Sydney waterfront. Wilf/Flickr
Nutrient-rich dust is critical, as well, in the oceans. “Dust depositions deliver nutrients that are in very, very scarce supply,” said Jason Neff (professor of environmental biogeochemistry at the University of Colorado). “Iron, phosphorous, nitrogen, carbon, and other micronutrients in the open ocean lead to higher marine productivity.” A case in point: A massive 2009 dust storm in Australia called Red Dawn (the largest loss of soil in history there), followed by another large dust storm, caused a huge spike in the growth of phytoplankton in the Tasman Sea because of high levels of iron in the wind-blown soil. Such phytoplankton blooms can pull substantial amounts of carbon dioxide from the atmosphere as the marine algae photosynthesize.
Dust influences climate
Dust clouds and the aerosol particles they contain have major impacts on climate in other ways, such as the blocking of sunlight headed for Earth. But this field of research is young and complex, and the science is lacking, adding uncertainty to future climate models. “The way that aerosols affect climate depends on their size, their color, their height in the atmosphere, how they interact with water vapor,” said Neff. “Aerosols are a tough area, because they can warm or they can cool depending on their composition and their location.”
Dust can cause disease
One proven impact from an increase in dust is on human health. In the U.S., an increase in dust storms is leading to many more cases of Valley fever, a fungus that lives in desert soils, becomes airborne as dust, and is then inhaled. The number of cases of Valley fever has increased dramatically in Arizona and California in recent years. In 2000, California and Arizona reported a total 2,757 cases of Valley fever. That number rose to 22,164 in 2011 following several extremely dusty years. The two states reported 11,459 Valley fever cases last year, with 57 fatalities occurring in Arizona. This sharp rise is due not only to increased wind and drought, but to increasing development, including the construction of utility-scale solar energy projects.
“At all of these solar ranches being put in out there, especially in the Mojave, there are huge areas being graded, all the vegetation is removed, and they keep it graded because they don’t want the vegetation to interfere with these solar panels,” said Antje Lauer (microbial ecologist at California State University in Bakersfield) who studies the disease. Changing patterns of drought and rain also favor the spores that cause Valley fever. Military training grounds in Texas and California create dust clouds so big they are visible from satellites.
In Japan, cases of Kawasaki disease — a rare malady that, among other things, causes inflammation of blood vessels, particularly coronary arteries — have been increasing. The bacteria or virus (no one is sure) can travel in events known as Yellow Dust — storms that blow in from the Gobi Desert.
Dust-filled winds that blow across a swath of central Africa during the dry season, from the Atlantic Ocean to the Red Sea, create something called the meningitis belt, so called because of the rash of outbreaks of the bacterial disease there.
How forest loss is leading to a rise in human disease
In the U.S., Phoenix and Tucson, Arizona are ground zero for giant haboobs — an Arabic term for dust storms — stirred by intense winds from thunderstorms that can be a mile high and engulf entire cities. Phoenix gets an average of three per year. Haboobs are the third-most dangerous type of weather in Arizona — after extreme temperatures and flash flooding — because they rise suddenly and without warning, greatly reducing visibility and causing traffic accidents. They also carry disease, bacteria, fecal matter from stockyards, herbicides, and pesticides and other pollutants harmful to human health.
The role that dust plays in the earth’s natural systems is only now coming into sharper focus as humanity’s impact on the planet intensifies. As researcher Aronson’s team put it in their study of Gobi Desert dust wafting over to California’s Sierras, “quantifying the importance of dust … is crucial for predicting how ecosystems will respond to global warming and greater use of the land.”
From: Yale Environment 360
November , 2017