Just How Close Are We to the Edge?

A paper came out in the journal Nature yesterday that contends we have reached the point of imminent environmental collapse.   Those of us who don't have a couple of hundred bucks to blow on a Nature subscription can still find plenty of reviews of the paper.

Let's start with this one from Simon Fraser University:

Using scientific theories, toy ecosystem modeling and paleontological evidence as a crystal ball, 21 scientists, including one from Simon Fraser University, predict we’re on a much worse collision course with Mother Nature than currently thought.

In Approaching a state-shift in Earth’s biosphere, a paper just published in Nature, the authors, whose expertise span a multitude of disciplines, suggest our planet’s ecosystems are careering towards an imminent, irreversible collapse.

Earth’s accelerating loss of biodiversity, its climates’ increasingly extreme fluctuations, its ecosystems’ growing connectedness and its radically changing total energy budget are precursors to reaching a planetary state threshold or tipping point.

Once that happens, which the authors predict could be reached this century, the planet’s ecosystems, as we know them, could irreversibly collapse in the proverbial blink of an eye.

“The last tipping point in Earth’s history occurred about 12,000 years ago when the planet went from being in the age of glaciers, which previously lasted 100,000 years, to being in its current interglacial state. Once that tipping point was reached, the most extreme biological changes leading to our current state occurred within only 1,000 years. That’s like going from a baby to an adult state in less than a year,” explains Arne Mooers. “Importantly, the planet is changing even faster now.”

The SFU professor of biodiversity is one of this paper’s authors. He stresses, “The odds are very high that the next global state change will be extremely disruptive to our civilizations. Remember, we went from being hunter-gathers to being moon-walkers during one of the most stable and benign periods in all of Earth’s history.

“Once a threshold-induced planetary state shift occurs, there’s no going back. So, if a system switches to a new state because you’ve added lots of energy, even if you take out the new energy, it won’t revert back to the old system. The planet doesn’t have any memory of the old state.”

Wired's Brandon Kiem adds this:

In the last few decades, scientists have found tipping behaviors in various natural environments, from locale-scale ponds and coral reefs to regional systems like the Sahara desert, which until 5,500 years ago was a fertile grassland, and perhaps even the Amazon basin.

Common to these examples is a type of transformation not described in traditional ideas of nature as existing in a static balance, with change occurring gradually. Instead, the systems seem to be dynamic, ebbing and flowing within a range of biological parameters.

Stress those parameters — with fast-rising temperatures, say, or a burst of nutrients — and systems are capable of sudden, feedback loop-fueled reconfiguration.

...Human activity now dominates 43 percent of Earth’s land surface and affects twice that area. One-third of all available fresh water is diverted to human use. A full 20 percent of Earth’s net terrestrial primary production, the sheer volume of life produced on land every year, is harvested for human purposes. Extinction rates compare to those recorded during the demise of dinosaurs and average temperatures will likely be higher in 2070 than at any point in human evolution.

Scientists informally call our current geological age the “Anthropocene,” and to Barnosky’s group this means we’re strong enough to tip the planet, radically changing regional climates and ecologies.

“Everything that happened the last time around is happening now, only more of it,” said Barnosky of the last ice age’s end and ongoing changes to Earth’s climate and biosphere. “I think the evidence makes it pretty clear that another critical transition or tipping point is very plausible within the next century.”

And this from the University of Helsinki:

Humanity uses 20 to 40 percent of the planet's basic production. Almost half of the planet's land area is taken up by agriculture or covered by buildings. A considerable part of what remains is pervaded by road networks. Consumption on this scale necessarily has a strong impact on the entire biosphere. Anthony D. Barnosky says:

—We may be seeing a radical change in all of the Earth’s ecosystems in the foreseeable future — even in places where people do not live.

The survey concludes that a state shift will likely occur in a few decades or in a hundred years at the latest. At an estimate, on 10 to 48 percent of the planet's surface, the current climate will disappear and be replaced with something that the current species have not encountered during their existence.

If we are to be able to anticipate changes and prepare for them, methods of predicting them will need to be improved considerably. The researchers propose ways to improve predicting and monitoring the state of the biosphere.

The central aims listed by the survey include curbing population growth and use of the planet's resources, and a swift move away from fossil sources of energy.