Sharks and rays pushed towards extinction by the shark fin trade are hot on the agenda at key wildlife talks.Read more
BBC Environment correspondent
Bigger is better, right? An ancient lore in biology, Cope’s rule, states that animals have a tendency to get bigger as they evolve. Evolution has cranked out some absolutely huge animals. But most of these giants are long gone. And those that remain are amongst the most threatened with extinction. Scientists now believe that while evolution favours larger creatures, extinction seems to favour the small. If you look at mammals, at the time of the dinosaurs, they were confined to rodent-sized scavengers living on the periphery. But 66 million years ago, the dinosaurs went and allowed the mammals to evolve into some really big creatures - 30 metre long blue whales, the ten tonne steppe mammoth and a giant ground sloth that looked a bit like a hamster but was the size of an elephant with enormous hooks for hands. Now, only the blue whale remains and these have been shown to have shrunk to half the size of their Pleistocene ancestors. So is it better to be small? Smaller animals need fewer resources and smaller territories. With the planet in such peril – are more animals going to start shrinking? Well, perhaps…new research shows that in 200 years’ time, the largest mammal might be the domestic cow. And of course the most successful organisms, in terms of biomass, on the planet are the smallest. Zoologist, Lucy Cooke examines the science of being small, and why size matters.
The Earth's biodiversity is decreasing at a faster rate than ever before. Why is this happening?
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Insects are the most varied and abundant animals outweighing humanity by 17 times, yet they are in decline in many parts of the world. Insects have been called the ‘glue’ in nature and are essential for the proper functioning of all ecosystems as pollinators, food for other animals, and recyclers of nutrients. This month the United Nations IPBES report said insect abundance has declined very rapidly in some places, and the available evidence supports a “tentative” estimate that 10% of the 5.5m species of insect thought to exist are threatened with extinction. Leading entomologists tell Tom Heap that insects have an image problem when it comes to conservation and the first step is getting people to care about these little creatures. We hear about the weird and wonderful world of some insect species that are declining in the UK, including mayflies and dung beetles and discover just how they contribute to the systems we humans rely on. The conversion of natural environments to create farmland is one of the main causes of the decline, with the use of pesticides, urbanisation and climate change also major factors. Tom asks global pesticide manufacturer Bayer about what they’re doing to help reverse insect decline and considers how we can practically make more space for insects. Producer: Sophie Anton Photo credit: Dr Beynon's Bug Farm