A study conducted in the United States at the Field Museum in Chicago has found that 52 of the most common and well known species of birds in that country have shrunk in size over a 38 year period. This is due to climate change, say the scientists at the University of Michigan who did the study.
This shrinking in size follows a rule in ecology called Bergmann’s rule which states that animals in cooler areas tend to be larger than those in warmer zones. Larger animals are able to keep warmer, which is the reason why animals in cold areas are larger.
As global warming affects the planet, animals now have to contend (deal with) rising temperatures. Some of them have responded by shrinking in size. This came to light when scientists studied over 70,000 specimens of birds collected over a 38 year period at the Field Museum (the bodies of animals and birds are preserved by museums so that they can be studied over years). That is when they discovered that some of the commonest birds in North America were shrinking in size. Studies done on deer, insects and fish also show similar patterns.
What does this mean for these species? Of course our planet has been through cycles of heating and cooling before, and many animals have evolved (or changed) to keep up with changes in their habitat in order to survive. The difference in the current cycle of global warming is that it is happening faster than ever before. So, animals may not be able to change fast enough.
Plus when species shrink, other things get affected. When an animal’s body shrinks, it may not be able to give birth to as many young as before – this may affect the size of a species’ population. Water dependent groups like amphibians may dry out faster during droughts as the water holding capacity shrinks.
It is possible that scientists haven’t yet fully understood how changes in size may affect the ability of animals to survive. This reflects the bigger problem with climate change – we aren’t always able to predict what will happen when the Earth’s temperatures keep rising. And that is the real danger.
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