字幕表 動画を再生する 英語字幕をプリント Have you ever heard the sound of frogs calling at night? For hundreds of millions of years, this croaking lullaby has filled the nighttime air. But recent studies suggest that these frogs are in danger of playing their final note. Over the past few decades, amphibian populations have been rapidly disappearing worldwide. Nearly one-third of the world's amphibian species are endanger of extinction, and over 100 species have already disappeared. But don't worry, there's still hope. Before we get into how to save the frogs, let's start by taking a look at why they're disappearing and why it's important to keep them around. Habitat destruction is the number one problem for frog populations around the world. There are seven billion humans on the planet, and we compete with frogs for habitat. We build cities, suburbs, and farms on top of frog habitat and chop forests and drain the wetlands that serve as home for numerous amphibian populations. Climate change alters precipitation levels, drying up ponds, streams, and cloud forests. As the Earth's human population continues to grow, so will the threats amphibians face. There are a variety of other factors contributing to the frogs' decline. Over-harvesting for the pet and food trade results in millions of frogs being taken out of the wild each year. Invasive species, such as non-native trout and crawfish, eat native frogs. Humans are facilitating the spread of infectious diseases by shipping over 100 million amphibians around the world each year for use as food, pets, bait, and in laboratories and zoos, with few regulations or quarantines. One of these diseases, chytridiomycosis, has driven stream-dwelling amphibian populations to extinction in Africa, Australia, Europe, and North, Central, and South America. On top of all these problems, we add hundreds of millions of kilograms of pesticides to our ecosystems each year. And these chemicals are easily absorbed through amphibians' permeable skin, causing immunosuppression, or a weakened immune system, and developmental deformities. Okay, so why are these little green guys worth keeping around? Frogs are important for a multitude of reasons. They're an integral part of the food web, eating flies, ticks, mosquitoes, and other disease vectors, thus, protecting us against malaria, dengue fever, and other illnesses. Tadpoles keep waterways clean by feeding on algae, reducing the demand on our community's filtration systems and keeping our cost of water low. Frogs serve as a source of food for birds, fish, snakes, dragonflies, and even monkeys. When frogs disappear, the food web is disturbed, and other animals can disappear as well. Amphibians are also extremely important in human medicine. Over ten percent of the Nobel prizes in physiology and medicine have gone to researchers whose work depended on amphibians. Some of the antimicrobial peptides on frog skin can kill HIV, some act as pain killers, and others serve as natural mosquito repellents. Many discoveries await us if we can save the frogs, but when a frog species disappears, so does any promise it holds for improving human health. Fortunately, there are lots of ways you can help, and the best place to start is by improving your ecological footprint and day-to-day actions. The next time you listen to that nighttime lullaby, don't think of it as just another background noise, hear it as a call for help, sung in perfect croaking harmony.