ected and the process repeats; this practice is
sustainable while population levels are low and time is permitted for
regrowth of natural vegetation; conversely, where these conditions do
not exist, the practice can have disastrous consequences for the
environment .
soil degradation - damage to the land's productive capacity because of
poor agricultural practices such as the excessive use of pesticides or
fertilizers, soil compaction from heavy equipment, or erosion of
topsoil, eventually resulting in reduced ability to produce
agricultural products.
soil erosion - the removal of soil by the action of water or wind,
compounded by poor agricultural practices, deforestation, overgrazing,
and desertification.
ultraviolet (UV) radiation - a portion of the electromagnetic energy
emitted by the sun and naturally filtered in the upper atmosphere by
the ozone layer; UV radiation can be harmful to living organisms and
has been linked to increasing rates of skin cancer in humans.
water-born diseases - those in which bacteria survive in, and are
transmitted through, water; always a serious threat in areas with an
untreated water supply.

Environment - international agreements
This entry separates country participation in international
environmental agreements into two levels - party to and signed, but not
ratified. Agreements are listed in alphabetical order by the
abbreviated form of the full name.

Environmental agreements
This information is presented in Appendix C: Selected International
Environmental Agreements, which includes the name, abbreviation, date
opened for signature, date entered into force, objective, and parties
by category.

Ethnic groups
This entry provides an ordered listing of ethnic groups starting with
the largest and normally includes the percent of total population.

Exchange rates
This entry provides the official value of a country's monetary unit at
a given date or over a given period of time, as expressed in units of
local currency per US dollar and as determined by international market
forces or official fiat.

Executive branch
This entry includes several subfields. Chief of state includes the name
and title of the titular leader of the country who represents the state
at official and ceremonial functions but may not be involved with the
day-to-day activities of the government. Head of government includes
the name and title of the top administrative leader who is designated
to manage the da