There is a growing body of evidence that many of the thousands of prescription and over-the-counter medications ultimately make their way into water bodies and drinking-water supplies. Typical wastewater treatment plants may not be effective at removing pharmaceuticals. This is because there are no regulations limiting the release of these substances in the environment and, as a result, the needed treatment technology may not have been investigated or implemented. Knowing the best treatment practices for removing pharmaceuticals from wastewater is important for protecting drinking-water supplies as well as organisms in marine and aquatic environments because many pharmaceuticals are designed to be effective at low concentrations. A new study shows that removal of pharmaceuticals from wastewater is possible, even at very low concentrations, depending on the specific treatment process, according to researchers reporting in Environmental Science: Water Research & Technology (January 2020). See also: Environmental toxicology; Freshwater ecosystem; Marine ecology; Water pollution; Water resources; Water treatment

Microplastics are raining down on national parks and other protected areas in the western United States at the rate of about 132 pieces of microplastic per square meter every day, according to a report in the journal Science (June 2020). Microplastics are plastic particles measuring less than five millimeters (approximately 0.2 inches) in length. The reported precipitation rate is similar to dumping about 300 million pulverized plastic water bottles (about 1000 tons) over the studied areas each year. Where do these particles come from? Sources mostly include fragments from virgin plastic pellets, polymer textile fibers, microbeads from personal care products and spray paints, as well as environmental degradation of waste plastic into smaller and smaller pieces over time. See also: Manufactured fiber; Paint and coatings; Plastic waste pollution; Polymer; Textile

Wildfires, also termed bushfires or forest fires, are currently devastating large swaths of land in Australia. Detrimental ecologic consequences of these uncontrolled combustions of forest fuels and vegetation are numerous. One of the most serious issues pertains to the survival of the koala, which is a small marsupial (pouch-bearing mammal) found only on that continent. Conservationists and scientists are concerned that the hundreds of fires presently raging in Australia, which were brought about by hotter and drier conditions exacerbated by anthropogenic climate change, may cause significant enough reductions in the population of koalas to threaten the continued existence of this species. See also: Australia; Forest fire; Global climate change; Global warming; Koala; Marsupialia

Biocontrol, or biological control, is the natural or applied regulation of populations of pest organisms—especially insects—through the role or use of natural enemies. In other words, biocontrol uses living organisms to reduce and eliminate pest abundance and damage. The agents through which biocontrol is accomplished are varied. For example, biocontrol agents can be consumers of pests; thus, herbivores are used to reduce weeds, whereas predators or parasites are employed to diminish the number of insect and other animal pests. In addition, pathogens and competitors that interact with pests are often utilized in biocontrol. Typically, agricultural and forest pests are the major targets of biocontrol. Notably, biocontrol operates as an alternative to the use of pesticides that may be harmful to the environment. See also: Agricultural science (animal); Agricultural science (plant); Agricultural soil and crop practices; Agriculture; Biological insect control; Forest; Forestry; Insecta; Parasitology; Pathogen; Predator-prey interactions; Weeds

For over fifty years, heat stabilizers, light stabilizers, and antioxidants have been added to polymers to maintain their material properties by preventing their degradation. This chemical adjustment is necessary to extend the life of products such as plastic pipes, paints and coatings, and automotive parts. More recently, additives with the opposite purpose have become available: They are designed to enhance the biodegradation of hydrocarbon polymers used in common products such as plastic bags. Biodegradation is the breakdown of organic compounds by microorganisms or other biological means to their inorganic mineral constituents, such as carbon dioxide (CO₂). Biodegradation additives would seem to be an elegant solution to the mounting environmental problem of plastic waste—except that recent research indicates they do not work. See also: Antioxidant; Biodegradation; Microbial ecology; Polymer; Polyolefin resins; Stabilizer (chemistry)

Charles Robert Darwin (February 12, 1809 – April 19, 1882) is one of the most celebrated and eminent scientists of the past few centuries, with his broadest and most notable influence arising from his theory of evolution by means of natural selection. Darwin’s remarkable investigations and insights obtained during his voyage on the HMS Beagle (1831–1836) led him to theorize about concepts of evolutionary biology and to develop revolutionary ideas related to adaptation and speciation. Although previous scientific thinkers had laid down some of the foundations for Darwin’s work, and others later expanded upon and more fully developed the scientific bases for his conclusions, Darwin set forth and formulated the controversial but coherent ideas about organic evolution that have impacted the world at large. His groundbreaking On the Origin of Species was originally published in 1859. Later, in 1871, Darwin argued in The Descent of Man and Selection in Relation to Sex that humans had evolved just as other organisms had, creating a storm of controversy that continues today. See also: Adaptation (biology); Animal evolution; Organic evolution; Plant evolution; Speciation

High within the coldest and driest continent, Antarctica, lies what may be an environment too hostile to support life, according to a team of scientists from Canada and the United States. They reported finding no evidence of microbial life in the dry permafrost and underlying ice-cemented soil of University Valley, located 1700 meters above sea level in the McMurdo Dry Valleys of Antarctica, which is mostly snow-free and never gets above freezing (Journal of the International Society for Microbial Ecology, January 2016). The single drier place on Earth is generally considered to be the Atacama Desert in Chile. See also: Antarctica; Desert; Hyperaridity and the dry limits of life; Permafrost

The world’s oceans and coasts provide a natural sink for excess carbon in the atmosphere. Scientists refer to carbon that is captured and stored this way as blue carbon. Well-known blue-carbon examples include mangroves and salt marshes—wetland ecosystems in which the soils may store carbon for thousands of years. An often-overlooked source of blue carbon, however, is large fish living in the open ocean, according to marine scientists reporting in the journal Science Advances (October 2020). Large fish are classified as being longer than 30 centimeters (12 inches) in length, and include such species as tunas, mackerels, sharks, and billfishes. See also: Carbon; Chondrichthyes; Mackerel; Mangrove; Salt marsh; Soil; Perciformes; Pisces (zoology); Tuna; Wetland

Monarch butterflies (Danaus plexippus) exclusively consume milkweed plants (genus Asclepia) both for nutrition and to help deter predators. Milkweed plants contain toxins that accumulate in the butterfly larva, or caterpillars, as the insects feed; those toxins then persist into the adult stage. Monarchs have evolved specific genetic mutations that protect their species from these poisons. Yet various organisms, including black-headed grosbeaks (a kind of bird) and eastern deer mice, as well as parasitic wasp and nematode (worm) species, can withstand the toxin and readily eat monarch butterflies. A new study has now shown how this is possible: all four predators, it turns out, have evolved monarch-like genetic mutations in their respective genomes that confer milkweed toxin resistance. The findings are a remarkable example of convergent evolution across distantly related organisms, whereby organisms independently evolve similar traits as they adapt to comparable environments and selection pressures. See also: Adaptation (biology); Convergent evolution; Evolution; Genetics; Gentianales; Insecta; Lepidoptera; Mutation; Plant-animal interactions; Poisonous plants; Toxin

Crown-of-thorns starfish or sea stars (Acanthaster planci; order Valvatida) are predatory marine invertebrates that feed on phytoplankton found on coral. They are native inhabitants of coral reefs in both the Indian Ocean and Pacific Ocean and are particularly common on the Great Barrier Reef, which is the largest living structure in the world, covering an area of more than 340,000 km² (131,000 mi²) off the northeast coast of Australia. Lately, crown-of-thorns sea stars are exploding in numbers, offsetting the ecosystem balance found in the waters of the Great Barrier Reef and causing marine investigators to fear severe degradation of the coral reefs, which are already under pressure from coral bleaching (the response of corals to environmental stress in which they eject the algae that live within the transparent coral tissue, making the white coral skeleton visible) and other effects of rising sea temperatures. See also: Asteroidea; Australia; Coral bleaching; Coral reef complexity; Ecological communities; Ecosystem; Marine ecology; Ocean warming; Reef; Severe coral bleaching endangers Great Barrier Reef; Valvatida