ARCATA, California, January 22, 2009 (ENS) – Death rates of old-growth trees in western U.S. forests have more than doubled over the past few decades, and the most likely cause of the trend is regional warming, finds new research to be published Friday in the journal “Science.”

Led by scientists with the U.S. Geological Survey, the research team found that the increase in dying trees has been pervasive. Tree death rates have increased across a wide variety of forest types, at all elevations, in trees of all sizes, and in pines, firs, hemlocks, and other kinds of trees.

Increasing tree mortality rates mean that western forests could become net sources of carbon dioxide to the atmosphere, further speeding up the pace of global warming, the scientists indicate.

Regardless of the cause, higher tree death rates could lead to substantial changes in western forests, said Phil van Mantgem, a USGS scientist and co-leader of the research team.

“The same way that in any group of people a small number will die each year, in any forest a small number of trees die each year,” said van Mantgem. “But our long-term monitoring shows that tree mortality has been climbing, while the establishment of replacement trees has not.”

The result is that forests have begun to lose trees faster than they are gaining them, said van Mantgem, a research ecologist with the USGS Redwood Field Station in Arcata, California.

Dead tree in Sequoia National Park, California (Photo by Nate Stephenson courtesy USGS)

These changes could change the suitability of forests for wildlife species, the scientists suggest.

They ruled out a number of possible sources of the increasing tree deaths, including air pollution, long-term effects of fire suppression, and normal forest dynamics.

Instead, increasing regional temperature was correlated with tree deaths.

“Average temperature in the West rose by more than 1° F over the last few decades,” said van Mantgem. “While this may not sound like much, it has been enough to reduce winter snowpack, cause earlier snowmelt, and lengthen the summer drought.”

The lengthening summer drought could be stressing trees, leading to higher death rates, he said. Warmer temperatures also might favor insects and diseases that attack trees. Some recent outbreaks of tree-killing bark beetles in the West have already been linked to warming temperatures.

“Tree death rates are like interest on a bank account – the effects compound over time,” said Nate Stephenson, also with the U.S. Geological Survey and research team co-leader.

“A doubling of death rates eventually could reduce average tree age in a forest by half, thus reducing average tree size,” said Stephenson, director of the USGS Sierra Nevada Global Change Research Program.

In some cases, increasing tree deaths could indicate forests vulnerable to sudden, extensive die-back, similar to forest die-back seen over the last few years in parts of the southwestern states, Colorado, and British Columbia.

“That may be our biggest concern,” said Stephenson. He worries that the trend observed by the research team is a prelude to bigger, more abrupt forest changes.

Complete findings appear in the article, “Widespread increase of tree mortality rates in the western United States.” Scientists with the U.S. Forest Service, University of Colorado, University of Washington, Oregon State University, Pennsylvania State University, Northern Arizona University, and the University of British Columbia contributed to this research.

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SAN FRANCISCO, California, April 9, 2008 (ENS) – A coalition of farmworker advocates and environmental groups filed a lawsuit against the U.S. Environmental Protection Agency Friday, seeking to force a halt to the use of four organophosphate pesticides.

Some of these pesticides have been detected in California’s rural schoolyards and homes, Sequoia National Park, and Monterey Bay.

The four organophosphates at issue in the case are methidathion, oxydemeton-methyl, methamidophos, and ethoprop. They are used primarily in California on a wide variety of fruit, vegetable, and nut crops.

“These four pesticides put thousands of farmworkers and their families at risk of serious illness every year,” said Patti Goldman, an attorney for Earthjustice, the environmental law firm that represents the coalition in the case, filed in U.S. District Court in San Francisco.

“It is inexcusable for EPA to allow use of pesticides that they know are harming people, especially children.”

Farmworkers are at risk of poisoning from
pesticides. (Photo courtesy OSHA)

The lawsuit alleges that the four pesticides were registered and are used in violation of the Federal Insecticide, Fungicide, and Rodenticide Act and the Endangered Species Act.

The plaintiffs seek a ruling that requires the EPA to make new re-registration eligibility decisions for the four pesticides.

The EPA has documented that children are especially susceptible to poisoning from organophosphates. Exposure can cause dizziness, vomiting, convulsions, numbness in the limbs, loss of intellectual functioning, and death. Some organophosphates also cause hormone disruption, birth defects, and cancer.

“Farmworkers and people living in and near agricultural regions, especially children, are at great risk of neurological and developmental damage due to exposure to these toxins,” said Dr. Margaret Reeves, senior scientist at Pesticide Action Network North America, one of the plaintiffs in the lawsuit.

The EPA has long recognized that the four organophosphates can poison farmworkers. Yet in 2002 and 2006, the agency decided that growers could continue using these poisons without considering the risks posed to rural children and families when these four pesticides drift into schoolyards, outdoor play areas, and homes.

“EPA knows that children in rural communities are exposed to these poisons, yet EPA has not even attempted to assess the risks resulting from such exposures,” said Shelley Davis, an attorney for Farmworker Justice. “By ignoring the risks that pesticides pose to our children, EPA has failed us all.”

The lawsuit was brought by Earthjustice and Farmworker Justice on behalf of Pesticide Action Network North America, United Farm Workers, Teamsters Local 890 in California, Sea Mar Community Health Centers, Pineros y Campesinos Unidos del Noroeste, Beyond Pesticides, Natural Resources Defense Council, Farm Labor Organizing Committee. California Rural Legal Assistance is also participating in the case on behalf of Moises Lopez, an individual farmworker in California.

The four poisons at issue in the lawsuit are all organophosphate pesticides derived from nerve gas developed during World War II.

They harm humans and wildlife by inhibiting the ability to produce cholinesterase, an enzyme necessary for the proper transmission of nerve impulses.

Symptoms include muscle spasms, confusion, dizziness, loss of consciousness, seizures, abdominal cramps, vomiting, diarrhea, cessation of breathing, paralysis, and death. Acute poisonings can cause long-term effects, such as permanent nerve damage, loss of intellectual functions, and neurobehavioral effects.

In addition to cholinesterase inhibition, which is common to all organophosphates, each of the pesticides targeted in the lawsuit poses unique risks to children, farmworkers, and wildlife.

Exposure to methidathion is believed to cause cancer. In 2008, the California Department of Pesticide Regulation listed methidathion as a toxic air contaminant because of methidathion’s carcinogenicity and neurotoxic effects.

Methidathion has been found in the air far from the farm fields where it is used, such as in Sequoia National Park.

In 2004, EPA estimated that 90 to 95 percent of methidathion use occurred in California. About 48,000 pounds of methidathion are applied in California annually, primarily on artichokes, oranges, almonds, peaches, and olives.

Oxydemeton-methyl is a reproductive toxin and is associated with decreased size and viability of offspring, decreased fertility, decreased size of reproductive organs and birth defects.

This pesticide is documented as causing die-offs in migratory birds. According to the EPA, oxydemeton-methyl poses severe risks to threatened and endangered species.

Approximately 130,000 pounds of oxydemeton-methyl were used in California in 2005, primarily on broccoli, lettuce, cauliflower, corn, cabbage, and brussels sprouts.

The EPA says methamidophos “poses one of the highest risks to workers of any organophosphate insecticide currently registered.”

It is one of the pesticides that EPA has designated for screening as a potential endocrine disrupting chemical.

This pesticide is believed to affect honey bees. A field study of the effects of methamidophos on honey bees demonstrated that the chemical can reduce the foraging activity of bees for a long time after application.

In 2000, approximately 640,000 pounds of methamidophos active ingredient were used in the United States. Most of this use was on potatoes, with lesser amounts used on cotton, tomatoes, and California alfalfa grown for seed.

Ethoprop is listed as a “known carcinogen” under California’s Proposition 65 Carcinogen List. The EPA has found that ethoprop poses cancer risks to farmworkers far exceeding what the agency considers acceptable for pesticides.

About 700,000 pounds of ethoprop are used in the U.S. annually, primarily on potatoes, sugarcane, and tobacco. When released into the environment, ethoprop degrades into other toxic chemicals that also pose cancer and non-cancer toxicological risks of concern.

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