Balance of nature: importance of ocean ecosystems (Introduction)

by David Turell @, Wednesday, November 18, 2020, 22:57 (11 days ago) @ David Turell

A study in loss of top predators and ocean effects:

"As sea otters declined (for reasons scientists are still trying to understand), their favorite prey—sea urchins—exploded in number. The voracious echinoderms not only mowed down the kelp but are also tearing apart and devouring the massive, slow-forming limestone reefs on which this seaweed grows, Rasher and his colleagues recently reported in Science. Rising ocean temperatures and acidification are compounding the damage.

"Restoring otter populations could rein in the urchins and help protect the larger ecosystem, and ecologists are increasingly interested in applying this idea more broadly. “Our study ... highlights the power of trophic cascades in nature and the potential for large predators to ameliorate some of the effects of climate change in the near term,” Rasher and his co-authors wrote. (“Trophic cascade” refers to the compounding effects of removing an organism from an ecosystem.) Many climate impact studies on species have not adequately acknowledged this kind of ecosystem complexity as a factor, according to Rasher and other scientists.


'The idea of restoring predators to blunt the impacts of warming has been simmering in ecology for decades. Fifteen years ago Christopher Wilmers, a wildlife ecologist now at the University of California, Santa Cruz, published studies looking at how warmer winters in Yellowstone National Park meant fewer elk foundering in deep snow and dying. The result was less early-winter carrion for the park’s many scavengers, such as grizzly bears and ravens, with dead elk bunching up at the end of relatively severe winters. After wolves were reintroduced in 1995, though, they became the main cause of elk mortality and created a steadier carrion supply that helped sustain other animals throughout the cold months. “Wolves provide this kind of temporal subsidy, where they’re making food for scavengers that would be overabundant at one time of year and underabundant at another and smoothing it out,” says Wilmers, who tracked Yellowstone wolf packs for four years.


"Rudolf created four habitats with pond water at present-day temperatures and four with heated pond water. He raised some tadpoles separated by species, some with mixed species, and others with mixed species and the dragonfly larvae. One species had lower survival rates in heated water when it was on its own—but when exposed to either competition or predation, the rates between heated and nonheated ponds were virtually equal. It could be that warmer conditions slow the larvae’s metabolism, prompting the predators to eat less, Rudolf says. Or the tadpoles might grow so fast in warmer water that it is harder for the larvae to capture them. “You might have reduced survival because of the direct effect of heat,” he says, “but [changes caused by] predation and competition can compensate for those direct losses. It buffers it out a bit.”


“'Everything we know about ecology is that as things get more complex, they change,” Rudolf says. That perspective is echoed in a soon to be published paper by University of Colorado Boulder ecologist Laura Dee, who points to the many indirect effects warmer temperatures can have on a species. These include increasing or decreasing prey, changing competitive abilities, shifting feeding rates and altering trophic cascades.


"In 2017 his team resurveyed the reefs’ status across the Aleutian archipelago and discovered that some had shrunk precipitously in just three years. Large areas that had been alive for centuries or millennia were crumbling and bleached, indicating urchins had recently killed them. Such devastation underscores the urgency of restoring balance to the ecosystem by bringing the otters back. And similar situations likely hold true for other ecosystems across the globe. Scientists still need to understand the reasons behind the otters’ disappearances, but Rasher Is hopeful. “Bringing the otters back would bring many ecological benefits,” he says, “and would also buy us time to get our act together on curbing carbon emissions.'”

Comment: Each ecosystem has its contribution to the whole. As the Earth has warmed in this recent past current sunspot cycles and now they may start cooling us, this article shows climate is related to how ecosystems are influenced, maintained or damaged. All the branches of the bush of life are interrelated through the common DNA code and how a food supply is precariously sustained.

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