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More than 1,000 dams have been removed across the United States because of safety concerns, sediment buildup, inefficiency or having otherwise outlived usefulness. A paper published today in Science finds that rivers are resilient and respond relatively quickly after a dam is removed. 

“The apparent success of dam removal as a means of river restoration is reflected in the increasing number of dams coming down, more than 1,000 in the last 40 years,” said lead author of the study Jim O’Connor, geologist with the U.S. Geological Survey. “Rivers quickly erode sediment accumulated in former reservoirs and redistribute it downstream, commonly returning the river to conditions similar to those prior to impoundment.”

A new study suggests that engaging in low intensity activities such as standing may not be enough to offset the health hazards of sitting for long periods of time. On the bright side, adding two minutes of walking each hour to your routine just might do the trick. These findings were published in the Clinical Journal of the American Society of Nephrology (CJASN).

Numerous studies have shown that sitting for extended periods of time each day leads to increased risk for early death, as well as heart disease, diabetes and other health conditions. Considering that 80 percent of Americans fall short of completing the recommended amount of exercise, 2.5 hours of moderate activity each week, it seems unrealistic to expect that people will replace sitting with even more exercise.

The decline of the world's large herbivores, especially in Africa and parts of Asia, is raising the specter of an "empty landscape" in some of the most diverse ecosystems on the planet, according to a newly published study. Many populations of animals such as rhinoceroses, zebras, camels, elephants and tapirs are diminishing or threatened with extinction in grasslands, savannahs, deserts and forests, scientists say.

An international team of scientists has used the 23-million-year fossil record to calculate which marine animals and ecosystems are most at risk of extinction today. In a paper published in the journal Science, the researchers found those animals and ecosystems most threatened are predominantly in the tropics.

A research team led by geoscientists from Brown University and the Marine Biological Laboratory has provided some crucial ground-truth for a method of measuring plant photosynthesis on a global scale from low-Earth orbit. The researchers have shown that chlorophyll fluorescence, a faint glow produced by plant leaves as a byproduct of photosynthesis, is a strong proxy for photosynthetic activity in the canopy of a deciduous forest. That glow can be detected by orbiting satellites and could be used to monitor global photosynthetic activity in real time.