Timing is everything.

In March of 1980, I was living in Washington state and a large earthquake in the vicinity of Mount St. Helens, an active volcano, rocked the  landscape and soon thereafter steam began to vent from the mountain.

By late April, a large bulge appeared on the north side of the mountain. On May 18, a massive eruption occurred, taking off the top 1,300 feet of the mountain. The devastation was awesome. Although 57 people died, geologists were able to warn nearby residents of the risk and many evacuated the area. The risk was imminent so people reacted.

We see the same behavior when a hurricane is likely to hit the coast and residents are warned. Many evacuate with just a few days warning.

With Earth Day just passed, I want to continue this theme of timing by considering what I think is the greatest threat to our earth: climate change. From the origin of humans about 150,000 years ago until 200 years ago, carbon dioxide levels in the atmosphere were steady around 275 parts per million (ppm). But with the industrial revolution, those levels have been steadily rising, now over 400 ppm.

The greenhouse effect produced by the ever-increasing carbon dioxide in the atmosphere is a major driver of global warming. These changes are incremental, occurring over many years so many people, including many politicians, do not see an imminent threat and hence feel no urgency to try to curtail carbon dioxide emissions.

Two recent articles sound the alarm for our bird populations with respect to climate change. In September of 2019, an article  appeared in the journal Science by Ken Rosenberg and colleagues. Using data from the Breeding Bird Survey and other long-term data sets, they found that North American bird populations have lost three billion birds compared to populations 50 years ago. That is a reduction of 29 percent. Of the 519 species analyzed, 57.4 percent are in a state of decline. Climate change is an important factor in driving these declines.

This month, an article by Christopher Trisos and colleagues appeared in the journal Nature. The researchers used temperature and rainfall data since 1850 to predict the environmental limits of 30,000 species of plants and animals from both the terrestrial and marine realms.

If global warming continues at its current pace, their model predicts not just isolated extinctions but the collapse of entire communities and ecosystems. These collapses may occur in the oceans by 2030 and in terrestrial habitats by 2050. These drastic extinctions would be devastating. The authors argue that if we can keep the earth from warming by 3.6 degrees, these abrupt losses of biodiversity can be averted. We have to get global warming under control.

Some people who oppose efforts to halt global warming argue that there have been times in earth’s history when the climate was much warmer than it is now. That claim is absolutely true. However, the rate at which the earth warms and cool was much more gradual than the rate in our current time. Ancient organisms had time to adapt to a warming or a cooling earth. The rate at which human activities are warming our globe is unprecedented.

Timing is everything.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at [email protected]

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