Salon.com > Biodiversity

Is there an actual tipping point for global warming?

Wed, 27 Mar 2013 15:56:00 +0000

Is there a chance that human intervention—rising temperatures, massive land-use changes, biodiversity loss and so on—could “tip” the entire world into a new climatic state? And if so, does that change what we should do about it?

As far back as 2008 NASA’s James Hansen argued that we had crossed a “tipping point” in the Arctic with regard to summer sea ice. The diminishing ice cover had moved past a critical threshold, and from then on levels would drop precipitously toward zero, with little hope of recovery. Other experts now say that recent years have confirmed that particular cliff-fall, and the September 2012 record minimum—an astonishing 18 percent lower than 2007’s previous record—was likely no fluke.

Death to the house cat!

Wed, 30 Jan 2013 22:12:00 +0000

Every few months, the fact that domestic cats are ruthless killers hits the news. This past summer it was the Kitty Cam, memorably explained by webcomic The Oatmeal, which saw nearly one-third of cats kill 2 animals each week on average. In 2011 a study found that domestic cats were responsible for nearly half of predation on baby gray catbirds (Dumetella carolinensis), a shy bird common in the mid-Atlantic and named for its cat-like call. And this morning, Nature Communications published a large analysis estimating how many animals are killed by cats annually in the US: 1.4-3.7 billion birds and 6.9-20.7 billion mammals each year (1).

Urban land area may triple by 2030

Wed, 19 Sep 2012 16:35:00 +0000

More than half of the world's expected nine billion people will live in giant urban expanses by 2030 as cities and their hinterlands occupy an additional 1.2 million square kilometers, thereby tripling in size. That's an additional 1.35 billion people living in cities, suggesting that urban areas that currently occupy roughly 3 percent of the planet's surface will continue to expand. By comparison, urban areas increased by just 58,000 square kilometers between 1970 and 2000.

In new work published in Proceedings of the National Academy of Sciences, urban environment researcher Karen Seto of the Yale School of Forestry and Environmental Studies and her colleagues first divided the global land area into discrete parcels and, using predicted gross domestic product growth, population growth and urban land area cover in 2000, they projected which parcels had a high or low probability of succumbing to citification over the next few decades. Using that model, 1.2 million square kilometers of land have probabilities higher than 75 percent of becoming citified and nearly six million square kilometers have some probability of going urban.