WHAT IS THE LATEST ON GLOBAL WARMING?

by Whit Gibbons


September 5, 2004


Was the Philadelphia Inquirer on target last month when they accused the Bush administration of having a "head-in-the-sand approach" about global warming? Or was a contrasting view given in the National Review Online more accurate in stating that the cost of taking steps to remedy global warming would outweigh the benefits of doing nothing?

Determining whether the economic costs are worth the environmental benefits of the United States' launching a conscientious offensive against global warming and its known and perceived causes is problematic. The issue swirls as much or more around politics, business interests, and nationalistic agendas as around the actual facts. What is true or not true about the environmental consequences of carbon dioxide emissions is controversial. But some facts related to global warming are incontestable.

Many species of plants unquestionably bloom earlier each year, and many animals indisputably breed earlier in the season now than they did a few years ago. Most scientists agree that global climate change resulting in warmer average temperatures around the globe is the underlying cause of the shifting reproductive patterns. By some measurements, the earth's temperature has risen more than one degree Fahrenheit over the last century and is steadily going up. A degree or so may seem trivial, but some ecologists consider the gradual warming of the globe to be responsible for observations being made about changing botanical and wildlife patterns.

One notable documentation of a change in seasonal activity of plants has been presented by Richard Primack and Abraham Miller-Rushing, biologists from Boston University who looked at the flowering dates of 229 individual plants that had been growing in the Arnold Arboretum in Boston for more than half a century. Their study used the long-term records of the time of flowering by particular plants on the grounds of the arboretum.

The investigators examined more than 60 species of plants, with the blooming records for some long-lived trees such as magnolia and dogwood going back more than a hundred years. Based on meteorological records for Boston, which not surprisingly encompass at least a couple of centuries, the average annual temperature has risen almost 3 degrees F since the late 1800s. One finding from the comparison of blooming dates was that during the last 20 years or so plants in the arboretum have flowered on average more than a week earlier than they did in the early 1900s.

Meanwhile, British scientists determined that flowers of nearly 400 species of plants for which records were available were blooming earlier than they once did. The average time of blooming in the period from 1990 to 2000 was advanced by more than 4 days when compared to blooming dates beginning in the 1950s. Some of the species flower as much as a month earlier now than they did in the last century. The results from both America and England are dramatic and should convince anyone that things are changing in the world.

I actually became aware of the advanced reproduction phenomenon a few years ago when Robert Kennamer of the Savannah River Ecology Laboratory showed me his two decades of data on South Carolina wood ducks. In short, wood ducks began to lay eggs earlier in the year during the 1990s than they did in the 20 years before. Nesting seasons, which typically began in mid-February in the 1970s, began in mid-January by the middle of the 1990s. From 1982 to 1996 alone, the average nesting date in the population advanced by about 10 days. Confirmed examples exist for other animal species responding to global warming, such as the elimination of lower elevation populations of pikas. These small, western North American relatives of rabbits require cool temperatures and many populations now live higher up mountain slopes than they did earlier in the century.

Is global warming a problem caused by greenhouse emissions that could be regulated by the ruling industrial nations to reduce the continued rise in temperatures predicted throughout the world? The point is likely to be debated nationally and internationally while temperatures continue to increase at least a few more degrees. But what cannot be argued is that many plants and animals are already changing their biology and reproducing earlier than ever before.



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