Historians aren't known for interdisciplinary collaborations. But Paul Hirt is getting environmental historians out into the field and working with anthropologists, ecologists and geographers. He hopes to increase their understanding of the complex interactions between humans and the landscape. --by Adelheid Fischer

The sky islands borderlands of the Southwest is a unique area harboring such a broad range of life that Conservation International has designated it a hotspot of global diversity. Once sparsely settled, the sky islands borderlands are now undergoing economic, ecological, and social upheavals. Environmental historian Paul Hirt is looking at the region's past to help citizens, businesses and governments manage its present and future. --by Adelheid Fischer

Nitrogen pollution from agricultural and urban runoff is a serious threat to ocean ecosystems. Nitrogen, in the form of nitrates, could generate algal blooms, create oceanic "dead zones" and kill coral, fish and shellfish in coastal zones. Researchers have discovered that small organisms in streams and rivers can filter out excess nitrogen before it reaches the oceans. However, overloading streams with too many nitrates reduces their filtering ability. --by Margaret Coulombe

When you visit the beach, the ocean always looks the same--but that doesn't mean it isn't changing. A new study has taken a comprehensive look at human impacts on marine ecosystems, including coral reefs, estuaries, and pelagic waters. The results show that none of Earth's oceans have escaped human influence. Now, oceanic maps from the study can help policy makers determine where human activities are most likely to cause negative effects. (Read the full story) --by Margaret Coulombe

The majority of people on Earth will soon live in megacities--urban areas with populations of 10 million or more. What will these future cities look like? And how will their populations meet the unique environmental challenges of the megacity? --by Margaret Coulombe

As the world's urban areas grow at an increasingly rapid pace, humankind must find ways to apply theoretical knowledge and scientific research more strategically--and more quickly. --by Jessica McCann

Why would anyone want to study ancient cultures? Charles Redman says that understanding the past is key to enriching the present and future. --by Jessica McCann