Xeric refers to an environment or habitat that is severely dry and lacking humidity and water due to limited rainfall.  Xeric shrublands are found in tropical, subtropical and temperate climate areas.  Animals in xeric environments are generally nocturnal to avoid moisture loss and include insects, reptiles, arachnids, birds and mammals.

Xeriscaping refers to a creative form of landscaping and gardening that uses xeric plant species to reduce or eliminate the need for additional water other than rainfall.  Many plant varieties are used for xeriscaping such as grasses, shrubs, succulents and annuals.  Advantages of xeriscaped gardens include low water consumption, low maintenance, better plant survival in hot weather, low cost, and they are visually interesting.

Xylene is a colourless, toxic liquid that is found in hydrocarbons, and occurs naturally in petroleum and coal tar.  It is a classified volatile organic compound (VOC) and is harmful to humans by inhalation and skin contact.  Xylene is commonly used as a solvent, paint thinner and in chemical production. 

Yard waste or garden waste, refers to solid organic waste that originates from residential gardens.  It is commonly composed of grass clippings, leaves, prunings, branches, weeds and other garden refuse.

In environmental terms, yield refers to the quantity of water that can be extracted from specific surface water or groundwater sources on an annual basis.  Most Australian states have methods in place to identify if surface water and groundwater allocations are within sustainable limits.

Yield factor refers to differences between countries in terms of productive land and waterways such as cropland, grazing land, forest and fisheries.  A yield factor may be used to calculate the global hectares of biocapacity (supply) and compare this to the global hectares of our ecological footprint (demand), in order to estimate the ecological overshoot.

Zero carbon is another term for ‘carbon neutral’, which refers to the measurement and balancing of carbon dioxide emissions released into the atmosphere, and the consequent offsetting of these emissions.  A zero carbon status is generally achieved by balancing the amount of emissions released from burning fossil fuels by producing a similar amount of renewable energy, or by only using renewable energy sources.  Zero carbon emissions can also be attained by paying others to remove or absorb emissions through practices such as planting trees or purchasing carbon credits.

Zero emission vehicles (ZEV) refer to vehicles that do not run on fossil fuel derived fuels, and do not produce any direct carbon emissions or air pollutants.  These vehicles generally run on electric batteries or hydrogen fuel cells.  Vehicles classified as zero emission do not factor in the emissions generated during the manufacturing process, which are higher than the emissions released during the vehicle's operating lifetime. 

A zero energy building (ZEB) is a building that does not consume energy from conventional power sources and does not produce any carbon emissions.  Zero energy buildings generally harvest their electricity on site using technologies such as solar, wind or hydro power.

Zero growth refers to the environmental concept that the global population should adopt a policy of zero population growth and zero economic growth in order to restore the earth’s natural environment.

Zero waste refers to the philosophy of avoiding, reducing, reusing and recycling waste in order to limit the amount of waste to landfill from households, and across all industries and organisations.

Zero Waste or no waste can be described as closed-loop cycle in which there is no emanating waste; waste becomes the resource for the next step in the cycle.

Zoning refers to the arrangement or land-use planning used by local government to partition land areas in suburbs, cities, or townships.  Zoning may determine permitted uses for land such as open space, agricultural, residential, commercial or industrial, as well as their associated characteristics, densities, building heights and locations, landscaping, parking and traffic lanes.

Zoocentric refers to the practice of focusing on animals and giving preference to animals above all other matters.