measure of how acidic or basic a substance is

area that contains a city

pollution that comes from many sources

pollution discharged from a single source

the movement of people from rural areas to cities

water that contains waste from homes or industry

rain, sleet, or snow that contains a high concentration of acids

when air pollution hangs over urban areas and reduces visibility

an area of open land often used for farming

when harmful substances build up in the air to unhealthy levels

all of the things a society builds for public use

amount of food that can be produced in a given area

type and amount of food a person consumes

the clearing of trees without replacing them

allowing more animals to graze in an area than the range can support

determining in advance how land will be used

increased temperature in a city

rapid expansion of a city into the countryside around the city

replanting of trees that have been cut down in a forest

illegal hunting

surface layer of soil

widespread starvation caused by a shortage of food

species not native to a particular region

a computerized system for storing, manipulating and viewing geographic data

movement of rock, soil and sand by wind and water

domesticated animals raised to be used on a farm or ranch, or to be sold for profit

partly decomposed organic material

the raising of aquatic organisms for human use or consumption

chemicals used to kill insects, weeds and other pests

bred and managed for human use

condition that occurs when people don't consume enough calories or eat a sufficient variety of foods

fresh water on Earth's land surface

number of different species in a given area

piece of DNA that codes for a specific trait

species native to a limited area

tourism that supports the conservation and sustainable development of ecologically unique area

any form of genetic material in cells of plants and animals

law designed to protect plant and animal species in danger of extinction

species not native to a specific area

built across rivers to control the river's flow

area of land that is drained by a river

safe to drink

organisms that cause illness or disease

an underground formation that contains groundwater

water found beneath the earth's surface in the spaces in sediment and rock

ability of rock or soil to allow water to flow through it

a flowing network of water

species critical to the functioning of an ecosystem

artificial lake