An ecosystem with plants and animals of unusual scientific and natural interest. It is a label given by UNESCO to help protect the sites

An impermeable rock layer preventing water from seeping into the aquifer from the ground surface directly above it. Instead, water travels down and across and eventually seeps into an unconfined aquifer farther away where the impermeable layer does not exist, often travelling large distances

A biological community of interacting living organisms and their physical environment. The living and physical components are linked together through nutrient cycles and energy flows

The study of the effects of toxic chemicals on biological organisms

The specific combination of different energy sources a country, for example, uses to meet its energy consumption needs