The Joshua tree (Yucca brevifolia) is a remarkable evergreen, treelike plant found only in the southwestern United States. It was named by Mormon settlers in the early 1800s. Upon seeing the limbs of this plant branching upwards to heaven, the Mormon travelers were reminded of the biblical prophet Joshua, who raised his arms in prayer for guidance to the Promised Land. The Joshua tree is the largest member of the Yucca genus of monocotyledonous trees and shrubs, which is placed in the agave family (Agavaceae; order Asparagales) or the lily family (Liliaceae; order Liliales), depending on the taxonomic system being used for classification. The height of the Joshua tree can reach 15 to 40 feet (4.6 to 12.2 meters) and its diameter ranges from 1 to 3 feet (0.3 to 0.9 meters). Life spans of 150 to 200 years have been documented for this resilient species, with some unverified ages of 500 to 1000 years being estimated. See also: Asparagales; Liliales; Monocotyledons; Tree

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

The species diversity and ultimate survival of amphibians, one of the major groupings of vertebrate animals, face tremendous challenges today for reasons that are still not entirely understood. Since the 1980s, the pace of amphibian extinction has been alarming, and almost 200 identified species have become extinct. About one-third of all amphibian species have seen dramatic declines in populations, and are now considered to be endangered or threatened with extinction. See also: Biodiversity; Endangered species; Extinction (biology); Extinction of species

Collectively, members of the class Amphibia are facing massive reductions in total numbers, and the overall biodiversity of amphibians across the globe is under threat. Scientists have determined that global climate change and habitat destruction are two chief factors responsible for some of the decreases observed in amphibian populations. However, another prime culprit has been discovered—specifically, chytridiomycosis. Chytridiomycosis is a disease caused by the waterborne fungal pathogen Batrachochytrium dendrobatidis (abbreviated as Bd). Since the 1980s, scientists have linked the chytrid fungus to the significant loss of much amphibian biodiversity in many locations around the world. More than 500 amphibian species have suffered total number losses as a result of chytridiomycosis, with at least 90 of these species becoming extinct. In addition, 124 species have suffered a 90% reduction in their populations, endangering their continued existence. Although all amphibian species are thought to be susceptible to chytridiomycosis, frogs and toads (order Anura) have been affected to the greatest degree. See also: Amphibia; Anura; Biodiversity; Endangered species; Extinction; Fungi; Global climate change; Mycology; Origins of modern amphibians

The Asian longhorned tick (Haemaphysalis longicornis), also known as the bush tick, is a troublesome parasitic species and is an important vector of disease agents. (Note that vectors are capable of biologically transferring a pathogen from one organism to another.) It also is becoming a problematic invasive species. Specifically, it is invading areas located far from its native region in East and Central Asia and is spreading within the United States. In particular, this arachnid is remarkable because female members can reproduce asexually without mating. Thus, scientists fear that the species will spread rapidly in locations where it has already invaded, thereby transmitting numerous diseases that are potentially harmful to humans and other animals. See also: Acari; Disease; Invasive species; Ixodides; Parasitology; Pathogen; Tick virus diseases; Zoonoses

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

Bats are members of the order Chiroptera, which is the second-largest order of living mammals. The geographic distribution of these flying mammals is tremendous as well, ranging from the limit of trees in the Northern Hemisphere to the southern tips of Africa, South America, and New Zealand. Within such a wide distribution, bats frequently encounter human populations. However, close contact between bats and humans is problematic with regard to disease ecology and epidemiology because bats are natural reservoirs (primary hosts) or intermediate hosts for numerous zoonotic pathogens—that is, infectious disease agents that are transmitted from animals to humans. Specifically, bats harbor more than 60 pathogenic viruses that can infect humans, including Ebola, Marburg, Nipah, Hendra, and rabies viruses. Bats also harbor various coronaviruses, including those responsible for severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and coronavirus disease 2019 (COVID-19). See also: Chiroptera; Coronavirus; Disease ecology; Epidemiology; Exotic viral diseases; Infectious disease; Mammalia; Pathogen; Rabies; Virus; Zoonoses

The dance language of honeybees (Apis mellifera) is a unique form of animal behavior and communication that was discovered by the zoologist Karl von Frisch (1886–1982) in the 1920s, which he continued to study through the 1960s and for which he was awarded a Nobel Prize in 1973. When foraging worker honeybees return to the hive with pollen or nectar, they perform dance movements to recruit other bees (follower bees) to visit a food source. The specifics of these movements convey information about the distance and direction from the hive to the food. This type of communication is highly unusual: Nonhuman animal communication typically concerns conditions and events immediately surrounding the instigator, whereas the honeybee dance language transmits information about remote events [scientists have documented bee dances about food sources up to 15 kilometers (9.3 miles) away from hives]. See also: Animal communication; Beekeeping; Ethology; Hymenoptera; Pollen; Pollination; Social insects

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