November 10, 2017

Last month, in October, scientists in Germany warned that flying insect populations are rapidly declining. A study published in the scientific journal PLOS One revealed that about 75 percent of the flying insects in German nature preserves have disappeared in less than 30 years. The decline in natural areas of Germany could spell doom for flying insects—and many other forms of life—around the world. Quick action is needed to stem this decline, a serious matter referred to somewhat less seriously as the “windshield phenomenon” by some biologists (meaning there are fewer dead bugs to clean off automobile windshields these days).

A recent study showed alarming reductions in populations of flying insects, a group of animals that includes bees, butterflies, dragonflies, mosquitoes, and fireflies (pictured here). Credit: WORLD BOOK photo by Don Stebbing

Scientists have described and named more than 1 1/2 million species (kinds) of animals. Of these, about 1 million are insects. Scientists discover thousands of new insect species every year, and they believe there are many more yet to be found. Insects form the basis of many thousands of food chains. About 60 percent of birds rely on insects as part of their diet, and many types of bats, fish, spiders, and other animals also rely heavily on insects. In addition, about 80 percent of wild plants rely on insects for pollination. Without insects, many of these animals and plants would die. Without those plants and animals, many other forms of life would die.

For the long-term study, scientists at the Entomological Society Krefeld set up malaise traps (tentlike traps made of fine mesh material that catches a wide variety of insects) in 63 German nature preserves over the course of 27 years. Malaise traps are generally set out for long periods and checked every 7 to 14 days. The traps were placed in grasslands, sand dunes, swamps, wastelands, and other areas where insects should have been plentiful. By measuring the weight of the insect catch—known as the biomass—from each malaise trap, researchers detected the sharp drop in flying insect numbers. The decrease from 1990 was alarming: an 82 percent decline at midsummer (when the populations should be most active), and a 76 percent decline throughout the year.

Pesticides and habitat destruction are thought to be the main culprits behind the decline. Jason R. Cryan, deputy director and chief of research and collections at the North Carolina Museum of Natural Sciences in the United States, noted that “Although the study was conducted entirely in Germany, these contributory factors are common globally, and thus we can expect that insect population declines of similar magnitude are occurring in other regions of the world.”

Earlier this year, the Entomological Society of America (ESA) published two formal position statements on endangered insect species and arthropod biodiversity. The statements mention the critical role insects play in healthy ecosystems and note that insects are often early indicators of ecological shifts. The ESA has called for enhanced research and increased conservation efforts to reduce habitat destruction and the use of pesticides.

The fossils of single-celled organisms found in Australia may be the oldest evidence of life on Earth. The fossils are 3.4 billion years old, only about 1 billion years younger than Earth itself, according to a report by a team of scientists from Australia and the United Kingdom. The team was headed by David Wacey of the University of Western Australia and Martin Brasier of the University of Oxford.

Scientists search for fossils. © Ken Abbott, University of Colorado at Boulder

Wacey and Brasier reported finding the microfossils in rock formed from sand that once covered an ancient beach in what is now Western Australia. The beach lay at the edge of what may have been one of the first sections of solid land to form.  At that time, most of Earth was covered by water.

Previously, what were believed to be the oldest known fossils, also found in Western Australia, were dated to 3.465 billion years ago. But a number of scientists have expressed doubts that these structures are fossils from that early in Earth’s history. Similarly, some scientists argued for more research to confirm that the structures presented by Wacey and Brasier actually represent ancient organisms and were not created by nonbiological processes.

There are an estimated 8.7 million species of plants, animals, and other organisms on Earth, according to a new tally of life on our planet.  Previous estimates of the number of species had ranged from 3 million to 100 million. The study was completed by scientists at Dalhousie University in Canada using a mathematical model based on the number of known species.

The scientists calculated that there are about 7.77 million species of animals; 298,000 species of plants; 611,000 species of fungi; 36,400 species of protozoa; and 27,500 species of chromists (organisms that are mostly ocean dwelling and make their own food using sunlight). However, only about 1.3 million species have actually been named and classified. The Dalhousie scientists estimated that 86 percent of all land-based species and 91 percent of all marine species remain unknown and so have not been described or catalogued.

Marine biologist Boris Worm, one of the study’s co-authors, compared Earth to a machine with 8.7 million parts in an article on the research in The Washington Post. “If you think of the planet as a life-support system for our species, you want to look at how complex that life-support system is,” Worm is quoted as saying. “We’re tinkering with that machine because we’re throwing out parts all the time.” The International Union for the Conservation of Nature and Natural Resources, a global federation of government and private conservation organizations, has estimated that at least one-third of Earth’s species are threatened with extinction.

Additional World Book articles:

• Why Species are Important (special report)