Human Activities and Environmental Problems

The rapid expansion of human activities places a heavy burden on ecosystems and causes serious environmental problems such as global warming, loss of biodiversity, and problems caused by introduced species.

Basic Knowledge

Global warming:
The phenomenon in which increasing greenhouse gases (CO₂, CH₄, N₂O, water vapor, and chlorofluorocarbons) raises Earth's average temperature. Since the Industrial Revolution, atmospheric CO₂ concentration has increased from about 280ppm to over 420ppm. This causes climate change, sea-level rise, extreme weather, and shifts in ecosystems.
Ozone-layer depletion: Chlorofluorocarbons destroy ozone (O₃) in the stratosphere, making it easier for ultraviolet radiation to reach Earth's surface. The ozone hole occurs over Antarctica. The Montreal Protocol regulated chlorofluorocarbons in 1987.
Acid rain: SO₂ and NO_x react with water vapor, producing rain with a pH of 5.6 or lower. It causes forest death and the death of fish in lakes.
Loss of biodiversity: Species become extinct because of development, agricultural expansion, climate change, overhunting, and other causes. The current extinction rate is 100–1000 times the natural rate. The Red List, prepared by the IUCN, classifies threatened species.
Introduced species (invasive alien species): Organisms from outside a region that are brought in by humans. They pressure native species and disturb ecosystems. Examples include largemouth bass, bluegill, raccoons, tall goldenrod, and common snapping turtles. Japan's Invasive Alien Species Act of 2005 designates specified invasive alien species.
Biomagnification: Harmful substances (DDT, PCB, and mercury) accumulate at higher concentrations at higher trophic levels. This caused Minamata disease (organic mercury).

Further Exploration

Among greenhouse gases, human-caused emissions of CO₂ are overwhelmingly large, and its contribution to global warming is greatest. However, one molecule of methane (CH₄) has about 25 times the greenhouse effect of CO₂, while N₂O (nitrous oxide) is about 300 times stronger. Livestock burps (methane) and agricultural fertilizers (N₂O) are therefore problems. The IPCC concluded that human-caused warming is “unequivocal.”
Biodiversity is understood at three levels.
① Species diversity (the existence of many different species)
② Genetic diversity (variation in genes within a species)
③ Ecosystem diversity (a variety of ecosystems, such as forests, wetlands, and coral reefs)
The Convention on Biological Diversity established an international framework in 1992. In 2010, COP10 (Aichi Targets) was adopted in Nagoya, and in 2022 the Kunming–Montreal Global Biodiversity Framework was adopted, including 30 by 30, the goal of conserving 30% of land and sea areas by 2030. Minamata disease, famous for biomagnification, was officially confirmed in 1956; methylmercury in wastewater from a chemical factory became concentrated more than 10,000-fold through the marine food chain.

Points to Note

① Global warming (CO₂ and other gases) and ozone-layer depletion (chlorofluorocarbons) are different problems. Chlorofluorocarbons are related to both, but their main causes differ. ② Introduced species also include organisms moved within Japan, such as from Honshu to Okinawa; they are not limited to species from other countries. ③ Biomagnification occurs with persistent, fat-soluble substances such as DDT, PCB, and mercury. ④ A Red Data Book and a Red List are not exactly the same: a list gives species names, while a book provides detailed information.

Practice

1. Name three representative greenhouse gases that cause global warming.
2. What is the phenomenon in which harmful substances accumulate at higher concentrations at higher trophic levels?
3. What Japanese law enacted in 2005 designates specified invasive alien species?