Scientists say that global warming isn't the only serious threat to humans. Another major threat is the falling numbers of insects and the extinction of many species. Scientists say that half of all insects worldwide have been declining since the 1970s. A new warning is that over 40 per cent of insect species could die out in our lifetime. Researchers said the number of insects is decreasing by 2.5 per cent every year. The scientists are calling it an "insect apocalypse". Many species of butterflies, bees and other bugs are now extinct. In the U.K. researchers say 23 bee and wasp species have gone extinct in the past century. Scientists say the apocalypse could trigger, "a catastrophic collapse of Earth's ecosystems".
Lead researcher Professor Dave Goulson said a lot of insects are being killed by pesticides used for farming and gardening. He said fewer numbers of insects might mean we cannot feed people. He told reporters: "Three quarters of our crops depend on insect pollinators. Crops will begin to fail. We won't have things like strawberries. We can't feed 7.5 billion people without insects." He said one of the most worrying trends is the decline of honeybees. In the USA, the number of honeybee colonies dropped from six million in 1947 to just 2.5 million in 2014. Professor Goulson warned people that: "We can't wait another 25 years before we do anything because it will be too late."