<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="548" name="human impacts" parent="1174" scope="The effects, intentional or unintentional, beneficial or harmful, direct or indirect, which human activities have upon the environment and living things."/><bt><term thcode="2" code="1174" name="topics" parent="1" scope="Themes, subjects, and concerns for which USGS information resources are relevant."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="1725" name="abandoned mines and quarries" parent="548" scope="Mines and quarries that have been abandoned and may expose harmful chemicals to the environment."/><term thcode="2" code="1354" name="deforestation" parent="548" scope="Reduction in the density of forest cover or tree canopy, typically by harvesting trees for human use or clearing land for other purposes such as agriculture."/><term thcode="2" code="1671" name="dredging" parent="548" scope="Removal of sediments from water bodies to aid navigation or to transfer material to another location."/><term thcode="2" code="629" name="land use change" parent="548" scope="Effect of changing land use patterns on ecological systems."/><term thcode="2" code="750" name="mining hazards" parent="548" scope="Dangerous conditions which result from the extraction of naturally occurring mineral deposits.  Includes tunnel collapses, fires, and explosions."/><term thcode="2" code="852" name="overfishing" parent="548" scope="Taking too many fish from an area beyond the capacity for the population to replenish its numbers. The balance of the ecosystem is upset, leading to long-term depletion of fish stock."/><term thcode="2" code="853" name="overgrazing" parent="548" scope="The practice of allowing animals to eat vegetation, especially ground cover, beyond the capacity of the plant population to replenish itself. Leads to erosion and other harm to the ecosystem."/><term thcode="2" code="1293" name="waste treatment and disposal" parent="548" scope="The chemical and physical methods to recycle or dispose of materials which, without treatment, are deemed to have no further value or are too contaminated to be used."/></nt><rt><term thcode="2" code="6" name="acid deposition" parent="66" scope="The process by which emissions, chiefly sulfur and nitrogen compounds, either react with the atmosphere when deposited on earth by precipitation of snow, rain, or fog with a pH of 5.5 or below, or settle out as acidic particles or gases."/><term thcode="2" code="769" name="contamination and pollution" parent="1174" scope="Introduction of harmful substances into the environment by human action or natural processes."/><term thcode="2" code="311" name="ecology" parent="650" scope="Study of the relations between living plants and animals and their environment."/><term thcode="2" code="320" name="ecotoxicology" parent="650" scope="Scientific study of causes, dispersal, and effects of contaminants on the environment."/><term thcode="2" code="345" name="environmental health (human)" parent="533" scope="Effects of the environment on human health."/><term thcode="2" code="384" name="fires" parent="101" scope="Combustion, marked by flames or intense heat, in natural settings, often ignited by lightning or human activities.  For fires set as part of natural resource management, use 'controlled fires'."/><term thcode="2" code="531" name="hazards" parent="1174" scope="Potential dangers from both natural processes (e.g., earthquakes, floods, and climate change) and human impacts on the environment."/><term thcode="2" code="602" name="invasive species" parent="797" scope="Plant, animal, or microbe species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm, or harm to human health."/><term thcode="2" code="1075" name="social sciences" parent="1019" scope="Sciences concerned with the structure and interrelationships of human societies, human institutions and organizations, and human culture over time."/><term thcode="2" code="624" name="subsidence" parent="451" scope="Settling, compaction, or caving in of land caused by subsurface mining, ground-water withdrawal, or pumping of oil and gas."/></rt></descriptor>