Article: The projected timing of abrupt ecological disruption from #climatechange — Nature

Click here to read the report (Christopher H. Trisos, Cory Merow & Alex L. Pigot). Here’s the abstract:

As anthropogenic climate change continues the risks to biodiversity will increase over time, with future projections indicating that a potentially catastrophic loss of global biodiversity is on the horizon. However, our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future. Here we use annual projections (from 1850 to 2100) of temperature and precipitation across the ranges of more than 30,000 marine and terrestrial species to estimate the timing of their exposure to potentially dangerous climate conditions. We project that future disruption of ecological assemblages as a result of climate change will be abrupt, because within any given ecological assemblage the exposure of most species to climate conditions beyond their realized niche limits occurs almost simultaneously. Under a high-emissions scenario (representative concentration pathway (RCP) 8.5), such abrupt exposure events begin before 2030 in tropical oceans and spread to tropical forests and higher latitudes by 2050. If global warming is kept below 2 °C, less than 2% of assemblages globally are projected to undergo abrupt exposure events of more than 20% of their constituent species; however, the risk accelerates with the magnitude of warming, threatening 15% of assemblages at 4 °C, with similar levels of risk in protected and unprotected areas. These results highlight the impending risk of sudden and severe biodiversity losses from climate change and provide a framework for predicting both when and where these events may occur.

Dead Gray whale Alaska. Photo credit: NOAA via Smithsonian Magazine

From Inside Climate News (Bob Berwyn):

A new study shows that as rising heat drives some key species extinct, it will affect other species, as well, in a domino effect.

Global warming is about to tear big holes into Earth’s delicate web of life, pushing temperatures beyond the tolerance of thousands of animals at the same time. As some key species go extinct, entire ecosystems like coral reefs and forests will crumble, and some will collapse abruptly, starting as soon as this decade, a new study in the journal Nature warns.

Many scientists see recent climate-related mass die-offs, including the coral bleaching of the Great Barrier Reef and widespread seabird and marine mammal mortality in the Northeastern Pacific linked to a marine heat wave, as warning signs of impending biodiversity collapse, said lead author Alex Pigot, a biodiversity researcher at University College, London. The new study shows that nowhere on Earth will escape the impacts.

“In the U.S., the southern states from Texas to Florida, the Appalachians and the West Coast are projected to be at particularly high risk, with between 20 and 40 percent of species facing conditions beyond anything they have previously experienced,” Pigot said…

In those regions many species live in small geographic areas under a narrow range of climatic conditions. As global warming heats their habitat to the point that it is intolerable, many species have no place to go. Some will go extinct, with a domino effect that affects scores of other species. If it gets too hot for bumblebees, for example, it affects the reproduction of plants. If it gets too warm for insects and reptiles, it affects food supplies for birds and mammals.

“I hope our predictions are wrong. But increasingly, what we’re observing around us are the signs of this happening,” Pigot said, referring to research showing how global warming affects individual species. “I think these studies are showing that many species are already living very near their thermal limits. Our results suggest that these losses are likely to involve multiple species near simultaneously rather than happening gradually, one species at a time,” he said.

At the current rate of warming, abrupt exposure events in tropical oceans will begin before 2030 and spread to tropical forests and higher latitudes by 2050. The risks decrease and arrive more slowly if global warming is capped at less than 3.6 degrees Fahrenheit, as per the goals of the 2015 Paris climate agreement, the study concluded.

“If we can avert the worst of the warming we can buy extra time,” Pigot said. “Even if we can get a few extra decades, it gives us time to work on expanding protected areas, or deciding on whether to try things like assisted migration and assisted evolution.”

Even an immediate curb on greenhouse gas emissions doesn’t preclude warming of up to 7 degrees Fahrenheit by the end of the century because the current amount of warming could be magnified by big increases of heat-trapping methane in the Arctic or by changes to cloud processes, he said.

The North Fork Valley, part of the service territory of Delta-Montrose Electric, has been known for its organic fruits and vegetables — including corn. Photo/Allen Best

From Harvest Public Media (Christina Stella):

In 2020, a stubborn enemy emerged for corn farmers across the Great Plains: drought. Today, about half of the U.S. is in drought, with large swaths of Nebraska, Iowa, Oklahoma, Kansas, and Illinois impacted.

A little dry or warm weather can be a boon for getting work done on the farm. Brian Fuchs, a climatologist at the National Drought Mitigation Center at the University of Nebraska-Lincoln says, for example, farmers in many pockets of the region enjoyed a rainless, temperate September, allowing them to finish harvest in record time and get a head start on prepping the farm for winter…

Yet these weather patterns create risky tradeoffs, posing another hidden risk for plants — hotter nighttime temperatures. That’s expected to become an increasing problem for corn crops that are just trying to get some sleep.

Corn has evolved to expect hot, sunny days and dark, cool summer nights.

During the daytime, the plant photosynthesizes, eventually turning sunlight, air, and water into corn.

At night, it stops that process and enters a state similar to rest — respiration — releasing carbon through its pores. An exhale at the end of a long day on the farm.

But adverse conditions like drought and heat can confuse the plant’s internal “schedule” and cause it to veer off course. Warm and dry evening conditions can especially pose risks to how efficiently the crop will function the following day.

“When nighttime temperature increases to where they’re uncomfortable, one of the first things that start to happen to them is that they start to respire more,” said Walid Sadok, an agronomist at the University of Minnesota.

“One of the consequences of that is, by losing that carbon, they reduce the yield potential, because that’s less carbon being invested to build [in the daytime].”

The plant also loses critical supplies of water, leading to poor pollination and dehydration. Sadok says the effects are similar to getting a bad night’s sleep.

“We noticed that the following day that photosynthesis — which is the ability to basically do work, capture that carbon from the atmosphere, use light energy — they are less good at that,” he explained.

The stakes are higher early in the growing season: just a few late spring evenings over 50 degrees can sabotage a farmers’ yield prospects. Fuchs says farmers do their best to plan, but conditions can change in a heartbeat.

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