Sean Caroll: An Ecology Lesson

Nautilus:

“Why is the planet green? Why don’t the animals eat all of the food? And what happens when certain animals are removed from a place? These questions led to the discovery that, just as there are molecular rules that regulate the numbers of different kinds of molecules and cells in the body, there are ecological rules that regulate the numbers and kinds of animals and plants in a given place. And these rules may have as much or more to do with our future welfare than all the molecular rules we may ever discover...

One major school of thought was that population size was controlled by physical conditions such as the weather. Smith, Hairston, and Slobodkin (hereafter dubbed “HSS”) all doubted this idea because, if true, it meant that population sizes fluctuated randomly with the weather. Instead, the trio was convinced that biological processes must control the abundance of species in nature, at least to some degree.

HSS pictured the food chain as subdivided into different levels according to the food each consumed (known as trophic levels). At the bottom were the decomposers that degrade organic debris; above them were the producers, the plants that relied on sunlight, rain, and soil nutrients; the next level were the consumers, the herbivores that ate plants; and above them the predators that ate the herbivores.

The ecological community generally accepted that each level limited the next higher level; that is, populations were positively regulated from the “bottom up.” But Smith and his lunch buddies pondered the observation that seemed at odds with this view: The terrestrial world is green. They knew that herbivores generally do not completely consume all of the vegetation available. Indeed, most plant leaves only show signs of being partially eaten. To HSS, that meant that herbivores were not food-limited, and that something else was limiting herbivore populations. That something, they believed, were predators, negatively regulating herbivore populations from the “top-down” in the food chain. While predator-prey relationships had long been studied by ecologists, it was generally thought that the availability of prey regulated predator numbers and not vice-versa. The proposal that predators as a whole acted to regulate prey populations was a radical twist...

Indeed, trophic cascades have been discovered across the globe, where keystone predators such as wolves, lions, sharks, coyotes, starfish, and spiders shape communities. And because of their newly appreciated regulatory roles, the loss of large predators over the past century has Estes, Paine, and many other biologists deeply concerned.”

Natalie Wolchover: Longer Time to Recover is a Warning Sign→

Atlantic:

“Systems that exhibit such “critical transitions” tend to be so complicated and riddled with feedback loops that experts cannot hope to calculate in advance where their tipping points lie—or how much additional tampering they can withstand before snapping irrevocably into a new state.

At Peter Lake, though, Carpenter and his team saw the critical transition coming. Rowing from trap to trap counting wriggling minnows and harvesting other data every day for three summers, the researchers captured the first field evidence of an early-warning signal that is theorized to arise in many complex systems as they drift toward their unknown points of no return.

The signal, a phenomenon called “critical slowing down,” is a lengthening of the time that a system takes to recover from small disturbances, such as a disease that reduces the minnow population, in the vicinity of a critical transition. It occurs because a system’s internal stabilizing forces—whatever they might be—become weaker near the point at which they suddenly propel the system toward a different state.”

Shrink to Fit→

David Malakoff, writing for Conservation (a good read pick):

“Around the planet, relatively large species are in big trouble—from lions and tigers and bears to cod, condors, and conifers. Even some heftier snails and salamanders are struggling. “Size matters,” says biologist Chris Darimont of the University of California, Santa Cruz, who notes that the assaults are coming from several angles. On one front, “a larger body size makes a species more vulnerable to all kinds of problems, from getting hunted by humans to habitat change.” One result: Nearly half of the world’s large “megafaunal” mammals—and more than half of the largest marine fish—are now considered vulnerable to imminent extinction.”

Natural selection at work.

Illustration by Philip Nagle

Is Conservation Extinct? A new look at preserving biodiversity→

Hillary Rosner, reporting for ENSIA:

“WWF’s Hoekstra likes to talk about “the pivot.”

Reactive and defensive almost by definition, conservation has long made its living by explicitly looking backward. It’s an approach that made perfect sense, for a time. “We wanted to restore a species so that it spanned the breadth of its historic range,” says Hoekstra. “We would look to the past and say, ‘We should have this much of this habitat back again, or it should look this way.’” But while this strategy may still work in certain specific cases, as an overarching vision it no longer fits. You can’t “dial back time” in a world of 9 billion people demanding water, food and energy.”

Interesting perspective that ecologists should stop using the 'past' to guide conservation, but rather look to the future or predict that future to direct today's conservation efforts. In a rapidly changing world, this approach makes sense.

Leading Canadian ecologist calls on scientists to recover policy influence→

Ron Meador, reporting for MinnPost: 

“David Schindler made plain in a talk Tuesday evening entitled “Letting the Light In: Providing Environmental Science to Direct Public Policy,” on the University of Minnesota’s St. Paul campus.

Schindler is a Minnesota-born engineer turned freshwater ecologist, a longtime leader in Canada’s environmental academy in part because his résumé includes deep involvement as a scientist in the battles over acid rain, eutrophication, dioxins and, more recently, the impacts of oil production from the Alberta tar sands.”

Why rabbits have white tails→

Daniel Cressey, reporting for Nature News Blog: 

“Dirk Semmann, an evolutionary biologist at the University of Göttingen in Germany, thinks he has the answer to this puzzle — and the evidence to back it up. Other theories hold that rump patches are warning to other animals, are sexually selected, or serve to show a predator that they have been spotted.

Semmann’s research suggests that these spots actually confuse predators because of their very noticeable nature. By focusing on the bright spot, the would-be predator ignores the larger body of the animal. Then, when the rabbit executes a sharp turn, the spot disappears and the predator has to readjust to focus on the camouflaged coat, losing vital seconds.”