biosphere -- the part of the Earth that supports life.

carbon footprint, annual --a measure of greenhouse gas carbon dioxide CO₂ released into the atmosphere per year due to one's purchases, resource consumption,  fossil fuel energy use (which releases CO₂ as a byproduct of combustion), and other relevant environmental impacts.  It includes both direct (e.g. gasoline powered auto travel) and indirect (e.g. electricity use from coal-fired power plants).  Per capita carbon footprints in affluent countries (in metric tons CO₂/ yr person) include: 20 for the USA, 17 for Canada,  around 9 for England, Germany, and Japan, and only 6 for France. 

climate change--refers to regional / global changes in climate over the last few decades and, more importantly, in the future.  Generally the world is warming--a trend that the UN's Intergovernmental Panel on Climate Change (IPCC) feels is (with 90 to 95% certainty) likely to have (in some part) been caused by human activities: most notably the combustion of fossil fuels leading to an enhanced greenhouse effect.  Climate change is most evident in the arctic, where polar ice, glaciers, and permafrost are melting.  Computer model projections call for both steadily increasing temperatures and changes / greater variability in regional weather patterns.  While humans may be able to adapt to climate change, ecologists are particularly concerned about the ability of many living things to do so. They note that the time scales needed for evolutionary adaptations for larger life forms are typically much longer than the decades / centuries over which this climate change is predicted to over.  The result could be widespread ecosystem disruption, extinction of many species, and loss of biodiversity.

deforestation--cutting trees and clearing forests, activities having both local and global negative environmental effects.  Locally wildlife habit and biodiversity is reduced; globally, since trees absorb carbon dioxide, both the absence of these trees and their burning (as in slash and burn clearing of land for farming operations) leads to increased atmospheric carbon dioxide which aggravates the global warming / climate change problem.

Earth's natural cycles--study of that very complex system, the roughly 8000 miles in diameter spherical planet Earth, is facilitated by considering its numerous subsystems--some of which are naturally conceptualized as cycles of matter moving within and between the Earth's biosphere, atmosphere, hydrosphere, and lithosphere.  Driven by input of solar energy, especially critical to life is the closed system cycling of six chemicals--providing individual oxygen, water, carbon, nitrogen, phosphorus, and sulfur cycles. The key to understanding the appearance of the Earth's surface landforms--and operating over a much longer time frame--is the rock cycle.  

ecological conscience--a term popularized by Aldo Leopold who connected it with treating the land right--in accordance with his land ethic.  More generally it involves feeling obligated to treat the natural habitat where one lives right: 1) not making a mess of it, and  2) not incurring ecological debt.

ecological debt -- refers to irreplaceable resources being consumed or natural cycles disrupted in an impossible or difficult to fix manner by human activities. While people today benefit from the consumption or the activity, the consequences of ecological debt incurred today will be left to future generations to deal with. Examples: hundreds or thousands of years from now people 1) might have to deal with highly radioactive nuclear waste that escapes repositories, a legacy of today’s nuclear generated electricity, 2) will no longer burn fossil fuels to power automobiles, the fossil fuel era will be over, the vast quantity of this huge resource, that it took nature millions of years to produce, having been consumed by human beings in a brief few hundred year period; 3) will suffer through uncomfortably hot summers, contend with incredibly strong hurricanes in coastal areas, and have memories of parts of the world long ago flooded by rising sea levels -- all resulting from the global warming , a legacy of long ago massive burning of fossil fuels and associated release of its carbon dioxide gas / greenhouse effect enhancing byproduct; 4) will live in a much less biologically diverse world--the result of human activity having caused the extinctions of millions of species!

ecosystem -- a self sustaining, interacting  natural community of animals, plants, and their physical environment. While matter cycles through such systems, energy moves in one-way (linear) fashion through the associated food chain. At its bottom, plants capture solar energy, are eaten by animals (herbivores and omnivores), who in turn are eaten by other animals (carnivores and omnivores) at the top. These are eaten by microorganisms (decomposers)-- by which time all of the energy that initially flowed into the system will have flowed back out as waste heat.  Each living component has a continuing, dynamic relationship with the others.  If numbers of species A fall, numbers of species B, which preys upon A, will similarly fall. With less predation of A its numbers  begin climbing, and likewise numbers of species B recover as well.

ecovillage--defined by the Ecovillage Network of Canada as "self-identified communities committed to living in an ecologically, economically, culturally and spiritually sustainable way." They are often composed of people who prefer living in a decentralized fashion: off centralized power grids, water and sewage systems.

environmental impact analysis -- a procedure for 1) collecting information about the proposed development, project or land use and its goals / objectives, 2) identifying possible impacts of its implementation in various areas (mainly environmental, but depending upon the scale of the project also perhaps cultural, economic, social, political, etc), 3) assessing impacts and identifying tradeoffs, 4) formulating, then examining other alternatives to the proposed development, with quantitative models and forecasts, 5) making recommendations including designating a preferred alternative that best meets goals / objectives while minimizing impacts / other concerns , and 6) making plans for monitoring performance. Legislation may require that this be done before certain projects can be carried out on government land.

geoengineering / planetary engineering--humans use technology to massively alter the global environment of Earth or another planet.  To combat Earth's manmade enhanced greenhouse effect induced global warming, geoengineering proposals have suggested 1) using space-based mirrors to reflect unwanted solar radiation back into space, 2) adding iron to the oceans to increase carbon dioxide absorption, and 3) adding sulfates to the atmosphere to create haze blocking solar radiation.  In the distant future, one can imagine similar (more massive) efforts to transform planets like Mars and Venus to make them habitable.

Green / Environmental Movement--a movement that blossomed in the 1960s with growing concerns about environmental pollution and manmade destruction of natural beauty, which, by the start of the 21st century had developed a political dimension with the formation of green parties in many countries. The chief goal of this movement is the development and maintenance of a sustainable society. It hopes to bring this about democratically by applying ecological wisdom and economic thinking that no longer ignores, but rather heavily factors in the environment.  Minimizing pollution, promoting efficient use of natural resources, recycling, shifting from fossil fuels to renewable energy, protecting biodiversity, and helping affluent western societies transition from wasteful, destructive multinational profit-minded corporate driven consumerism / globalization to more environmentally sound, ethical, socially just, sustainable economies are important goals of this movement.

greenhouse effect --an important heat trapping mechanism. It works as follows: The sun’s visible light readily passes through either glass in a greenhouse or the Earth’s atmosphere. But upon striking a surface (soil, the ground, etc) and being absorbed, the energy that is reradiated by this surface as it heats up is different in wavelength from visible sunlight. Specifically it is called infrared radiation and has a longer wavelength. This infrared radiation does not so easily pass back out through the glass or atmosphere. In the case of the atmosphere, it is trapped by greenhouse gases -- most notably water vapor and carbon dioxide. So with more energy coming in from the sun than escapes back to space, a temperature increase results.

greenhouse effect, enhanced --In the last 100 years human fossil fuel combustion has put extra carbon dioxide into the atmosphere and enhanced this greenhouse effect. The result has been a slight increase in average global temperature, less than one degree Celsius.  With human activities pouring increasing amounts of carbon dioxide into the atmosphere, the world continues to warm. Based on current trends, computer models project future global warming of one to six  more degrees in the next century. Such warming is expected to bring significant global climate change, disrupting both natural ecosystems and human society / comfort. People can keep this projected disruption to a minimum by using fossil fuel energy more efficiently and increasingly switching from it to renewable energy.

greenhouse gases, other--carbon dioxide gets the attention, but humans also put increasing amounts of other greenhouse gases into the atmosphere--notably methane, released in agricultural activities and many times as potent. A greater concern is that warming of the Arctic will free methane trapped in permafrost --which some feel could be catastrophic! 

green national product -- a proposed index of sustainable economic welfare obtained by making certain adjustments to gross national product -- most notably ones that factor in depletion of natural resources and any long-term environmental damage associated with economic activities.

hydroelectric--electricity generated when falling water turns a generator.  Employing well known technology, it is renewable and inexpensive. Its prospects for growth are not as great as other renewable sources such as solar or wind, since (especially in the developed world) most rivers with large hydropower potential have already been dammed. 

natural capital -- is to be distinguished from manmade capital and human capital. Natural capital includes natural resources (air, water, soil, forests, minerals, fossil fuels, fish, etc) and the biodiversity of natural living ecosystems (grasslands, wetlands, ocean coral reefs, etc.)

nonrenewable resources--irreplaceable natural resources whose amount--for all practical purposes--is limited. Examples include fossil fuels (coal, oil, natural gas, etc), iron ore, copper, etc.  For the fossil fuel most important to the global economy--oil--speculation abounds as to whether world oil production has already peaked and is about to decline (as pessimists claim), or won't peak for another two decades or so (as optimists believe.)  Unless replacements / alternatives can be readily phased in, economic disruption spurred by higher prices for dwindling resources could accompany decline in production of such non-renewable resources.

nuclear energy--can be traced to the energy with which the tightly bound constituents of nuclei (the central massive parts of atoms) are held together.  Certain processes (called nuclear reactions) can liberate this energy in an amount E equal to the "missing mass" m involved, times a constant (which equals the speed of light) c squared--that is, Einstein's famous equation E=mc².  In comparison to chemical reactions--such as burning of fossil fuels --nuclear reactions unleash about one million times more energy per amount of mass involved.  So the nuclear fission reactions associated with splitting apart the (heavy) nuclei in one gram of uranium unleash as much energy as the combustion of a ton of coal!  Such fission reactions are the basis for nuclear power plants which produce around 20% of the electricity used by the United States (in some countries, notably France, the % is much greater).  Since such power plants do not produce greenhouse gases they are touted by some as a way to combat global warming. Others object to them for three reasons: 1) they produce long-lived radioactive waste which must be stored for thousands of years until it decays to safe levels, 2) concerns about the potential for associated radioactive mischief, perhaps involving terrorists, and 3) high costs of constructing them, given public safety concerns. 

overshoot and collapse -- a phenomenon often seen by ecologists in studying ecosystems. It occurs when the numbers of a certain species dramatically rise, exceed the carrying capacity of the ecosystem, and then fall suddenly. Their numbers can recover eventually, provided the demands on the environment were not such that the carrying capacity is permanently degraded.

ozone depletion--refers to manmade chemicals--most notably chlorofluorocarbons--that destroy upper atmosphere ozone which shields life on the ground from dangerous ultraviolet radiation.  International agreements reached in the early 1990s have apparently helped stabilize such ozone levels and the problem is not viewed with the serious alarm it once was.

pesticides--substances used to kill or control pests: organisms which interfere with human well being or activities (agricultural, in particular). They are classified according to the type of pest they are used on (e.g. insecticides, herbicides, fungicides, etc.)  While such use of naturally occurring substances goes back thousands of years, the first manmade pesticide to be widely used was the insecticide DDT, developed in 1939.  Like DDT, many pesticides can poison humans and damage the environment. By the 1960s--with the publication of Rachel Carson's book Silent Spring, it was recognized that DDT interferes with bird reproduction. It is now banned in many countries.  A new generation of pesticides--some of which are biological agents, instead of manmade chemicals-- promise less environmental impact.

population and family planning--refers to efforts to limit the number of children in a family.  The goal of such planning is to insure that all children born 1) are truly wanted, and 2) can be adequately supported and raised to adulthood given the resources available. While implemented at the individual family level, policies can be formulated at the national government level. This has most notably occurred in China, where the "One Child Policy" was adopted in 1979 to address population growth concerns.  Family planning services typically focus on promoting and providing access to birth control devices (contraceptive pills, condoms, etc). Where those fail, counseling as to whether to use an abortion clinic's services may be provided.  More draconian options include forced sterilization--which has been used in the United States to prevent mentally deficient people from reproducing.

population growth concerns -- Reportedly since the days of the Babylonians in 1600 BC.--when the human population was around 35 million-- people have worried about the possibility of a growing population exceeding the capability to feed people. Typically the former grows exponentially (1, 2, 4, 8, etc) while the latter increases but arithmetically (1,2,3,4, etc) -- as Thomas Malthus pointed out in 1798. A few years later in 1804 the human population reached one billion; by 1927 it had doubled to two billion. The doubling time of 123 years is consistent with an average annual growth rate of around 0.6 % per year. The next doubling to four billion took roughly 47 years, consistent with an average annual growth rate of around 1.5 % per year. The growth rate peaked around 1970 at 2.1 % per year. By 2005 it had fallen to 1.2 % per year, and the human population stood at 6.5 billion people. If that growth rate continues, by 2050 there will be 11.7 billion people; if the growth rate continues to fall, as projected, by 2050 there will be 9.1 billion people. How many people can the planet support? Answers vary. Many environmentalists feel that the current population is excessive and that human activities are altering the global climate and causing dangerous disruptions of natural cycles. Currently enough grain is grown to feed 10 billion people a vegetarian diet.