Aquaculture, the farming of fresh or saltwater plants or animals, is a rapidly expanding industry, currently accounting for more than a quarter of global fish and seafood production.

The EarthTrends searchable database currently includes a limited number of population and demographic indicators that forecast data up to 2050 (see below). These data are produced by the United Nations Population Division.

The ranking of countries according to various indicators can be useful in bringing the world's attention to bear on important differences in national conditions and challenges. Although there remains no universally accepted ranking of the most environmentally-friendly countries, two recent rankings, the Environmental Sustainability Index (ESI) and the Environmental Performance Index (EPI) go some way towards filling this gap and providing an objective picture of national differences in environmental status and stewardship.

Renewable forms of energy, or renewables, constitute a suite of energy production alternatives to nuclear power and the burning of fossil fuels (coal, oil, and natural gas). Sources of renewable power generation include wind power, solar energy, geothermal heat, hydroelectricity, and biofuels (e.g., ethanol).

Here at the World Resources Institute (WRI) there are several projects that provide information about renewable energy:

In addition to the country-level data provided on EarthTrends, regional and classification aggregates calculated by WRI are available for most of the variables within the EarthTrends searchable database. These calculations require assignment of individual countries to specific regions or groups.

In general, data on water issues are sparse, particularly with respect to water quality and pollution; informative time series are often difficult to construct. Existing data typically come from national or regional studies undertaken by independent researchers, or data are the result of comprehensive surveys performed (infrequently) by international organizations. Since data have disparate sources, data collection and calculation methodologies may vary.

As of 2005, the most populated countries according to estimates from the United Nations Population Division are, in descending order, China, India, The United States, Indonesia, Brazil, Pakistan, Bangladesh, The Russian Federation, Nigeria, and Japan.

'Sustainable Development' is an official term, coined in a 1987 report produced by the World Commission on Environment and Development. Entitled Our Common Future or the Brundtland Report (after the Chairman of the commission, former Norwegian Prime Minister Gro Harlem Brundtland), the report defines 'sustainable development' as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs"; this includes economic growth, environmental protection, and social equity. The entire report can be found on-line at the United Nations Department for Economic and Social Affairs Division for Sustainable Development website.

One of the most frequently utilized gauges of poverty is the percent of people within a country or region that live on less than one dollar ($1) a day [a]. About 1/5 of the Earth's population, or 1.1 billion people, currently live on less than $1 a day [1]. Nine of the ten countries with the largest percent of people in this category are in Africa; Madagascar, Sierra Leone, Burundi, Gambia, Niger, Zambia, Central African Republic, Nigeria, and Mali have 49% to a staggering 73%, respectively, of their populations living in extreme poverty conditions. Between 1981 and 2001 the percent of total people in Sub-Saharan Africa living on less than $1 a day increased 93%, from 164 million to 316 million [1].

Carbon Dioxide (CO2) is the most widely known "greenhouse gas". Over the 20th century, global atmospheric CO2 levels have steadily risen from just below 300 parts per million (ppm) in the early 1900's to current levels of approximately 380ppm. General consensus within the scientific community ascribes this increase to the burning of fossil fuels (coal, oil, and natural gas). In 2000, the world emitted some 24 billion metric tons of CO2 from the burning of fossil fuels. This means roughly 3.9 metric tons were emitted on a per capita basis worldwide. However, the disparity between the developed world and the developing world is substantial; per capita, people residing in developed countries emitted 11.2 metric tons, nearly 6 times their counterparts in the developing world where the per capita average equaled 1.9 metric tons.