The impact of climate change on birds

As our readers know, we consider climate change the most important environmental problem of the 21st century.  All other environmental issues pale in comparison to climate change because most other problems are exacerbated, if not caused by climate change.  For example, when native plant advocates demand that we destroy healthy trees storing tons of carbon dioxide, we know that they are not benefiting native plants which will be less well adapted to a changed climate.  The many projects that are destroying healthy trees chip the wood, which releases the stored carbon into the atmosphere as carbon dioxide as the wood decays over time.

The environmental reviews of these destructive projects try to respond to this criticism of their projects by making a number of bogus claims.  For example, they claim that they intend to replace all the trees with native trees, although the horticultural requirements of native trees will prevent their survival where most non-native trees now thrive.  They also claim that the mythical new native trees will compensate for the loss of the carbon stored in the existing urban forest, based on their belief that young trees store carbon at a faster rate than old trees.

Now we have a new study which has overturned this assumption.  Thirty-eight scientists from all over the world participated in a study of 670,000 trees from 403 tropical and temperate species of trees.  They have reported their findings in Nature magazine:

“Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density.” (1)

In other words, we now have empirical evidence that large, old trees store far more carbon than young trees.

The impact of climate change on birds

Since native plant advocates often claim that their destructive projects benefit birds, let’s examine that claim in the context of climate change.  How is climate change making life difficult for birds?  That’s our topic today.

Female Snowy Owl.  Creative Commons
Female Snowy Owl. Creative Commons

We start with a report that snowy owls are being seen in the continental United States, in places far outside their normal range, such as Little Rock, Arkansas and northern Florida.  At Logan Airport in Boston, more than 75 snowies have been captured and relocated during last fall’s migration season, an unprecedented number.  Airports are attractive to grass-eating birds such as geese as well as raptors hunting for small mammals, such as owls and hawks because they are surrounded by vast, open fields.  Airports are dangerous places for both birds and airplane passengers, so this isn’t good news for anyone.

Snowy owls are enormous birds (20-27 inches tall and 54-66 inches wingspan) with white feathers that blend with their usual home in the Arctic.  So what are they doing so far south?  Nobody really knows, but there are theories.  One of those theories is that there was a sudden surge in the population of lemmings in the Arctic which is the preferred prey of the snowies.  That sudden increase in their food source may have caused a surge in the population of snowies and now they must disperse to parts unknown to find what they need to eat.  We will revisit that theory latter in the context of climate change; the article about the impact of climate change on bird populations (see below) reports that the population of lemmings has declined, suggesting that the snowies are moving south in search of food.

What happens when snow turns to rain?

As the climate warms, places where winters brought snow in the past are now rainy.  Think of what that means to birds sitting on nests in the open.  Snow doesn’t penetrate the down of chicks as much as rain does.  A nestling that was kept dry in the snow is now soaked to the skin.  Brrrrrrr…can you feel for that bird?

Magellanic Penguin.  Creative Commons
Magellanic Penguin. Creative Commons

A colony of Magellanic penguins in Argentina has been studied for decades by a researcher who now reports that climate change is taking its toll on that colony:

“’Rainfall is killing a lot of penguins, and so is heat,’ said P. Dee Boersma, a University of Washington scientist and lead author of the study, ’And those are two new causes.’” (2)

The penguin chicks are most vulnerable about a week after hatching, when their parents have quit protecting them round-the-clock.  After about 6 weeks, they develop more waterproof plumage.  In the past, only about one-third of chicks survived to leave the nest, most often as a result of predation and starvation.  Heavy storms killed penguins in 13 of the 28 years of the study.  Extreme heat events have recently taken a toll.  The population of breeding pairs in the colony has declined by 24 percent since 1987.

Rain where snow was the more usual winter weather-pattern is also known to have taken a toll on the peregrine falcon population in the Canadian Arctic.

Disrupting the food chain in the Arctic

Yale Environment 360 recently published a report about the impact of climate change on birds in the Arctic. (3) Here is a long, depressing list of specific impacts on many species of birds as a result of climate change in the Arctic:

  • As we have reported, polar bears around Hudson Bay are starving because the bay is no longer freezing long enough for them to hunt for seals on the ice.  They have turned to eating birds’ eggs.  Can you blame them?
  • The rising temperature in the Arctic has increased the population of mosquitoes.  Some birds are dying from blood loss.  This may be hard to imagine if you haven’t visited the Arctic. We can tell you from experience, that the air is black with mosquitoes on a typical summer day in Alaska.
  • Contrary to the opinion of the researchers studying snowy owls, the researchers interviewed by Yale Environment 360 say that the population of lemmings and other prey has declined which has reduced populations of peregrine falcon, ptarmigan, jaeger, skua, etc.  A researcher explains that early, deep snow provides the insulation needed for successful breeding of lemmings.  Without this insulation, the population has decreased significantly. 
  • As spring arrives earlier, snowshoe hares may not be changing their white fur fast enough to escape predation, which will reduce that population over time as fewer hares survive to breed in the future.  The hare is an important source of prey for the raptors.
  • Gulls scavenged the seal hunts of polar bears in the past.  With receding ice and reduced hunting opportunities, this food source has decreased and what remains is often contaminated with mercury.  These factors have combined to result in an 80% decline in the gull population since the 1980s.
  • When weather conditions are unseasonal and extreme at the start of the nesting season, birds often skip the nesting season altogether.  Such a sensible choice has been observed by scientists in several locations.

The article ends on a modest note, by reminding us how little we know about birds and the limitations of the research that is done on their populations.  Some of the population changes that have been observed could be short-term.  There is much variation in nature from which we cannot accurately extrapolate.

How could local native plant “restorations” benefit birds? 

The projects demanded by native plant advocates will destroy tens of thousands of healthy, old, large trees that are expected to live at least 200 more years and store much additional carbon during that period.  These trees will release tons of the greenhouse gases causing climate change when they are destroyed.  Climate change is clearly not benefiting birds.  How can native plant advocates continue to claim that the projects they demand will benefit birds?  It is a cruel fiction that these projects will benefit birds.

We are reporting about studies of birds in polar regions today.  Climate change at the poles is presently more visible and extreme than it is locally.  Assuming that we continue to do nothing, we can expect similar changes in our neighborhood in the near future with similar impacts on the birds.


(1) N.L. Stephenson, et. al., “Rate of tree carbon accumulation increases continuously with tree size,” Nature, January 15, 2014.
(2) Henry Fountain, “For Already Vulnerable Penguins, Study Finds Climate Change Is Another Danger,” New York Times, January 29, 2014.
(3) Ed Struzik, “Northern Mystery: Why Are Birds of the Arctic in Decline?” Yale Environment 360, January 22, 2014

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