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Distance and Adaptation on Darwin Day

Today is Darwin Day, and so it seems appropriate to take a look around our own world today and consider issues of adaptation and selection. These days, selection forces are increasingly artificial – even for plants and animals that we might refer to as wildlife.

audubon graphsThe National Audubon Society has been conducting something called the Christmas Bird Count for generations. It’s an activity that gathers observations of birds at the same time of year, across North America, using large numbers of volunteers who are knowledgeable in bird identification.

This week, Audubon published the results of a study of shifts in the location of wintertime bird populations over the last four decades. What the study found is that 58 percent of the 305 bird species surveyed have shifted their ranges more than 100 miles to the north since the late 1960s.

Many bird species have shifted northward much further than that. The wintertime range of the purple finch has shifted northward by 433 miles. The wild turkey, while not as graceful a flier as the finch, is not far behind, with a 407.6 mile northward shift.

What’s striking about these two species of birds is that they’ve expanded the furthest to the north because they’re among those most able to – the purple finch because of its migratory habits and the turkey because of its ability to exploit the margins of human habitation. Other species, such as the meadowlark, have not shifted far to the north because they’ve not been able to. Northern grasslands have fewer resources than southern grasslands, and meadowlarks live primarily in grasslands, unable to adapt to other areas very well. So, meadowlarks haven’t been able to shift north very well, and their population has decreased by 70 percent.

These differences suggest that while some forms of wildlife are adjusting to climate change in a way that will enable them to survive, other forms aren’t. This is Darwinian selection we’re observing, but with a twist – it’s human caused, and artificially accelerated. The Audubon study confirms both that significant climate change is taking place, and that it will have a significant negative impact on biodiversity.

It’s a big problem, but it won’t do any good to just shrug our shoulders and sigh. We need to adapt our human culture to these changing circumstances – that’s been humanity’s strongest evolutionary advantage, after all. There are lots of things that you can do to cut back on your use of energy, and reduce greenhouse gas emissions. You can also contribute to organizations like Audubon that work to protect areas of natural habitat, so that wildlife has the space it needs as it adapts to climate change.

Even kids can help – by nagging their parents, turning off extra lights, and collecting their pennies. Audubon has a Pennies for the Planet activist system for kids who care enough to do their share. Every little bit counts.

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