As if climate change weren't peril enough, a group of international scientists finds that other compounding factors - population growth, energy use, habitat destruction - are hastening the day when the planet faces a biological breakdown. It's a dire warning that world leaders can't ignore.
The findings may sound like more of the same: Climate change is raising the world's temperatures and producing wholesale shifts in ocean levels, vegetation and wildlife. But the panel of 22 researchers from five countries have expanded the lens.
Other human-caused changes are afoot. A global population of 7 billion is set to rise past 9 billion by mid-century. At the same time, humans are taking up more space, building cities and expanding farms from the present 43 percent of the world's surface toward the 50 percent mark. It keeps going: fossil fuels spew more carbon dioxide into the skies, which drip acid into the oceans, diminishing underwater life. It's all attributable to human activity.
It's a depressing scenario, but, the authors insist, not a hopeless one. That's because government leadership, energy innovation and environmental initiatives could stem the worst of it. We may be fouling the planet, but we can fix it too.
The report is timed for a U.N. conference on sustainable development known as Rio+20 in Rio de Janeiro beginning June 22. The gathering marks the 20 years from the first "Earth Summit" that brought 172 countries together to map out programs on climate change and biodiversity.
Not much has happened in the last two decades, at least not enough to stem a dire slide in the planet's health, according to the scientists who compiled the report.
The specter is a possible repeat of past planet-altering events such as the last ice age, which featured a warm, cold and then warm cycle that led to extinctions and a permanent change in the Earth's biology.
"Humans are now forcing another such transition, with the potential to transform Earth rapidly and irreversibly into a state unknown in human experience," wrote the group whose primary author was UC Berkeley professor Anthony Barnosky.
Still, the preventive steps won't be easy sells, especially as governments totter in economic slowdown. All of the changes will need to be major to be meaningful. Among them: a sharp drop in population growth, a task complicated by social customs, religion and health care; thriftier energy use, which requires investment and changed habits; and more protection of unexploited areas to safeguard wildlife, never easy as development spreads.
It's a tall order. But there isn't any alternative. The U.N. conference will test not just whether leaders have read the report's warning, but whether they're willing to take serious action.