Field experimentField experiments are experiments carried out outside of laboratory settings. They randomly assign subjects (or other sampling units) to either treatment or control groups to test claims of causal relationships. Random assignment helps establish the comparability of the treatment and control group so that any differences between them that emerge after the treatment has been administered plausibly reflect the influence of the treatment rather than pre-existing differences between the groups.
Nutrient pollutionNutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Raw sewage is a large contributor to cultural eutrophication since sewage is high in nutrients.
Ecosystem collapseEcological collapse An ecosystem is considered collapsed when its unique biotic (characteristic biota) or abiotic features are lost from all previous occurrences. Ecosystem collapse causes ecological collapse within a system; essentially altering its stability, resilience, and diversity levels. It is, however, possible to reverse through careful restoration, and is thus not completely equivalent to species extinction.
Climate change and infectious diseasesGlobal climate change has resulted in a wide range of impacts on the spread of infectious diseases. Like other ways in which climate change affects on human health, climate change exacerbates existing inequalities and challenges in managing infectious disease. Infectious diseases whose transmission can be impacted by climate change include dengue fever, malaria, tick-borne diseases, leishmaniasis and Ebola virus disease. For example, climate change is altering the geographic range and seasonality of the mosquito that can carry dengue.
TaigaTaiga (ˈtaɪɡə; тайга́; relates to Mongolic or Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, and larches. The taiga or boreal forest has been called the world's largest land biome. In North America, it covers most of inland Canada, Alaska, and parts of the northern contiguous United States.
