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Scientists have spent over 20 years documenting how the sizes of species around the world have been changing. In recently published research, several of them concluded that animals and plants are shrinking in response to the rise in global temperatures.

"Some of the most iconic species, like polar bears, are the captivating examples, but some of the organisms that have changed the most are grass, birds, and salamanders," explained Dr Bickford of the National University of Singapore, one of the study’s lead authors.

This is not just a modern phenomenon. It has happened throughout the Earth’s history. By examining fossils, which act as a record of the species that have lived on the Earth, it has been shown that when there have been hotter periods in the Earth’s past, animals and plants shrunk in size.

"Body size, temperature, and metabolic rate are all inter-dependent," explained Dr Bickford. As plants get smaller, adapting to warmer, harsher environments, animals that rely on them for food either need to eat more plants or get smaller themselves. The evidence suggests that the animals are shrinking, and this in turn impacts on animals higher up in the food chain. Predators that feed on these animals also reduce their body size so that they don’t waste too much energy on catching larger amounts of smaller prey to maintain a bigger body.

Even though the world’s species seem to be able to adapt to survive in an increasingly hotter climate, the adaptations might actually upset the intricate web of interactions between species. This is because ecology is not simple; some animals might not be affected while others might be affected severely. This would result in imbalances in the food web, jeopardising species and possibly even entire ecosystems.

About the scientist: Dr David Bickford

I grew up camping and spending a good deal of time outdoors and was always curious about nature. Having a background in math and the sciences, I quickly became motivated to study more about the fascinating plants and animals I was learning more about - kind of a snowball effect; the more I learned, the more I wanted to find out!

I have always been interested in evolution and ecology and have motivations to help society by protecting our natural resources and promoting ideas about sustainability. After having dedicated myself to focusing on the tropical areas of the planet where both biodiversity and threat to ecosystems were concentrated, I quickly became interested in myriad of species of reptiles and amphibians that I could find, catch, or observe in the tropics.

I am still highly motivated to learn and explore ideas – and as much as possible, I prefer to do so in a context that has an application that can benefit humanity.