How global warming could cause animals to shrink

Sep 27, 2011
Calanus propinquus, one of the organisms investigated in this study © Pete Lens, British Antarctic Survey

The way in which global warming causes many of the world’s organisms to shrink has been revealed by new research from Queen Mary, University of London.

Almost all cold-blooded organisms are affected by a phenomenon known as the ‘temperature-size rule’, which describes how individuals of the same species reach a smaller adult size when reared at warmer temperatures. But until now, scientists have not fully understood how these size changes take place.

Writing in the journal The American Naturalist, Dr Andrew Hirst and colleagues from Queen Mary’s School of Biological and Chemical Sciences explore this unusual shrinking effect in more detail, and show conclusively how it occurs.

Funded by the Natural Environment Research Council, the study was carried out using data on marine planktonic copepods. These tiny crustaceans are the main animal plankton in the world’s oceans and are important grazers of smaller plankton and a food source for larger fish, birds and marine mammals.

By gathering together more than 40 years of research studying the effect of temperature on these organisms, their results show that growth rate (how fast mass is accumulated) and development rate (how fast an individual passes through its life stages) are consistently decoupled in a range of species, with development being more sensitive to temperature than growth.

Dr Hirst explains: “We’ve shown that growth and development increase at different rates as temperatures warm. The consequences are that at warmer temperatures a species grows faster but matures even faster still, resulting in them achieving a smaller adult size.

“Decoupling of these rates could have important consequences for individual species and ecosystems,” he added.

The team’s findings suggest that rates fundamental to all organisms (such as mortality, reproduction and feeding), may not change in synch with one another in a warming world. This could have profound implications for understanding how organisms work, and impact on entire food webs and the world’s ecosystems.

Although the team’s findings disagree with earlier assertions of many macro-ecologists, they clearly explain the smaller sizes associated with the ‘temperature-size rule’. They hope their work will help those investigating the potential impacts of climate change on the natural world.

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User comments : 5

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Shootist
2.3 / 5 (6) Sep 27, 2011
How global warming could cause animals to shrink


Yes. The dinosaurs were so small in the hothouse that was the Triassic.
Crucialitis
4.2 / 5 (5) Sep 27, 2011
How global warming could cause animals to shrink


Yes. The dinosaurs were so small in the hothouse that was the Triassic.


Yes.. what with those higher levels of oxygen to support larger sizes. But no, it's implying global warming so it's all a crock, isn't it?
Nanobanano
5 / 5 (2) Sep 27, 2011
Shootist:

Different mechanism.

For the dinosaurs, both the temperature and the 02 levels were much higher. I was about to write about ancient giant insect species before I read your post.

You see, size is also proportional to 02 levels, and it has even been demonstrated by experiment that some aspects of gigantism can be replicated in pressurized chambers with elevated air pressure and elevated 02 levels.

So that is a different mechanism.

though admittedly, if we keep burning fossil fuels we actually DO decrease 02 levels, but only by a very tiny amount relative to the amount of 02 currently in the atmosphere. So this mechanism would hardly matter on human time scales with regards to global warming.

But essentially if you increase the amount of 02 in the atmosphere, but not to the point of toxicity, then you increase the efficiency of lungs, gills, and hearts in organisms, which allows them to grow bigger and stronger.
Nanobanano
5 / 5 (1) Sep 27, 2011
Large reptilians and amphibians thrive in the tropics because they absorb the extra heat from their environment. But in the mid and upper lattitudes reptians are very small, or non-existant, because they are cold blooded and the environment cannot provide enough heat for them.

For mammals, the opposite is true, with a few odd exceptions. The historical an fossil records show that cold environments favor gigantism in mammals because of the effect of maximizing the volume to surface area ratio allows the moderation of temperature better. Think Woolly Mammoth, Sabretooth cat, and short tooth bears, etc.

So these mechanisms CAN theoretically be related under the right environmental conditions, (i.e. if we burn up enough oxygen to significantly change the 02 levels in the atmosphere it would also increase CO2 and therefore temperature,) but they are not necessarily related in the real world.
freethinking
1.8 / 5 (5) Sep 27, 2011
Add this to the list of what global warming will do. According to global warming believers, gold supplies will be affected by global warming

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