Science Monday, June 11, 2012
Local ecosystems may hint at global shift, report says
The global ecosystem may be headed for a tipping point, possibly in the next 50 to 100 years, reported a group of scientists in the journal Nature this week.
Local ecosystems “are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds,” they wrote, noting that there is evidence that the “global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence.”
It is not yet clear what could lie on the other side of that tipping point, how soon it might occur or how to tell when it is imminent, but researchers called for a improved forecasting to answer those questions — as well as addressing the “root causes of how humans are forcing biological changes.”
Those changes include the 43 percent of Earth’s land surface that humans have developed, farmed or logged — likely to reach 50 percent by 2025, according to the scientists’ estimates. Other studies have shown that the actual area those human activities impact is much, much larger.
The study comes in a special issue of Nature put out ahead of the Rio+20 conference in Rio de Janeiro later this month, which is held on the 20th anniversary of the 1992 Rio Earth Summit on sustainable development.
■ This month’s meeting will also try to continue the work begun at the historic 1992 conference — work that has been going quite slowly, in the estimation of another article in this week’s Nature. Though the conference ended up spawning a series of international agreements on some of the most pressing environmental issues over the next two decades, in terms of actually delivering on the goals of curbing biodiversity loss, stabilizing greenhouse gas emissions and slowing desertification, the journal gives the international community “F"s across the board.
■ Perhaps underlining those failures, monitoring stations throughout the Arctic are reporting carbon dioxide levels of 400 parts per million or higher in the atmosphere, a milestone researchers were expecting as levels of the greenhouse gas continue to rise. Globally, carbon dioxide levels are at 395 ppm, far past the 350 ppm threshold that scientists have said is the safe upper limit for avoiding the worst impacts of climate change. Pre-Industrial Age levels have been estimated at about 275 ppm. The 400 ppm figure in the Arctic is expected to drop slightly over the summer as plants grow and absorb carbon, but scientists, including those at the National Oceanic and Atmospheric Administration’s Earth System Research Lab in Boulder, expect carbon dioxide levels to continue to rise, passing 400 ppm globally within a few years.
■ If you found all this depressing, don’t worry; none of it will matter in about four billion years. That is when the Andromeda galaxy, currently hurtling toward our own Milky Way galaxy at about 250,000 mph— or fast enough to travel from here to the moon in an hour—will finally collide with the Milky Way. This will result in a single merged, much different-looking galaxy, NASA scientists announced Thursday. Though our solar system, including the Earth, will survive, it will be flung to a different, less central neighborhood of the new galaxy. For now, the two galaxies remain friendly, if distant, neighbors, with Andromeda still a safe 2.5 million light-years away. The projections come from measurements from the Hubble Space Telescope and computer simulations based on the data.