Natural events such as volcanic eruptions or earthquakes are part of the dynamic quality of Earth and its ecosystems. Weather-related events, including drought, fire, flooding, storms, and infestations, can harm or enhance ecosystems. Geological events such as volcanic eruptions, earthquakes, and landslides cause changes to ecosystems. Healthy ecosystems will respond by adapting over time. Natural Phenomena and Ecosystems 5.1 VOCABULARY sapwood

Pollutants in Ecosystems 5.2 VOCABULARY pollutant acid precipitatiion pH scale Pollutants are substances introduced into air, water, soil, or food in concentrations that threaten the health or survival of organisms. Pollutants can be grouped according to the part of the environment they affect (air, water, or land, for example). Human populations are producing more pollution than can be degraded in the biosphere. Many pollutants are not natural, but are a result of human technology.

Bioaccumulation and Biomagnification 5.3 VOCABULARY bioaccumulation biomagnification pesticide DDT (dichloro-diphenyl- trichloroethane) parts per million (ppm) heavy metals endocrine-disrupting compounds (EDCs) Many pollutants bioaccumulate in organisms. Bioaccumulation is the buildup of chemical substances within the tissues of organisms over time. Biomagnification of pollutants can occur in organisms at the top of food chains or food webs. These pollutants include pesticides like DDT, heavy metals, and other endocrine-disrupting compounds such as PCBs.

The Impacts of Human Industry on Ecosystems 5.4 VOCABULARY soil degradation deforestation Human activities affect ecosystems. Human industries such as agriculture and forestry often impact ecosystems in negative ways. Negative impacts include soil degradation, spraying chemical pesticides, and deforestation. Traditional ecological knowledge and wisdom (TEKW) promotes sustainable use of the environment.

Changing the Balance in Ecosystems Natural phenomena impact the natural balance (equilibrium) in ecosystems. These phenomena range from mild earthquakes that affect few organisms to disastrous tsunamis that wipe out entire islands. Humans introduce many pollutants which affect the growth and survival of organisms. Human activities affect ecosystems. Industries like agriculture and forestry often impact ecosystems negatively. Traditional ecological knowledge and wisdom (TEKW) from First Nations people promotes sustainable use of the environment. 5 CHAPTER

Changing the Balance in Ecosystems Activity With a partner, choose an ecosystem and brainstorm a list of all the natural phenomena you can think of that could affect that ecosystem. Examples of ecosystems include rainforests, ponds, deserts, etc. Afterward, describe the impact of each phenomenon on your ecosystem. Is it positive or negative? In what way? Compare your list with Table 1 on page 109 and Table 2 on page 111 in the textbook. 5 CHAPTER

Changing the Balance in Ecosystems 5 Key Ideas Natural phenomena impact the equilibrium in ecosystems. Pollutants affect the growth and survival of organisms. Human activities affect ecosystems. CHAPTER