Ecological footprint in the context of "World Wide Fund for Nature"

A city is a human settlement of a substantial size. The term "city" has different meanings around the world and in some places the settlement can be very small. Even where the term is limited to larger settlements, there is no universally agreed definition of the lower boundary for their size. In a narrower sense, a city can be defined as a permanent and densely populated place with administratively defined boundaries whose members work primarily on non-agricultural tasks. Cities generally have extensive systems for housing, transportation, sanitation, utilities, land use, production of goods, and communication. Their density facilitates interaction between people, government organizations, and businesses, sometimes benefiting different parties in the process, such as improving the efficiency of goods and service distribution.

Historically, city dwellers have been a small proportion of humanity overall, but following two centuries of unprecedented and rapid urbanization, more than half of the world population now lives in cities, which has had profound consequences for global sustainability. Present-day cities usually form the core of larger metropolitan areas and urban areas—creating numerous commuters traveling toward city centres for employment, entertainment, and education. However, in a world of intensifying globalization, all cities are to varying degrees also connected globally beyond these regions. This increased influence means that cities also have significant influences on global issues, such as sustainable development, climate change, and global health. Because of these major influences on global issues, the international community has prioritized investment in sustainable cities through Sustainable Development Goal 11. Due to the efficiency of transportation and the smaller land consumption, dense cities hold the potential to have a smaller ecological footprint per inhabitant than more sparsely populated areas. Therefore, compact cities are often referred to as a crucial element in fighting climate change. However, this concentration can also have some significant harmful effects, such as forming urban heat islands, concentrating pollution, and stressing water supplies and other resources.

Sustainable living describes a lifestyle that attempts to reduce the use of Earth's natural resources by an individual or society. Its practitioners often attempt to reduce their ecological footprint (including their carbon footprint) by altering their home designs and methods of transportation, energy consumption and diet. Its proponents aim to conduct their lives in ways that are consistent with sustainability, naturally balanced, and respectful of humanity's symbiotic relationship with the Earth's natural ecology. The practice and general philosophy of ecological living closely follows the overall principles of sustainable development.

One approach to sustainable living, exemplified by small-scale urban transition towns and rural ecovillages, seeks to create self-reliant communities based on principles of simple living, which maximize self-sufficiency, particularly in food production. These principles, on a broader scale, underpin the concept of a bioregional economy.

The biocapacity or biological capacity of an ecosystem is an estimate of its production of certain biological materials such as natural resources, and its absorption and filtering of other materials such as carbon dioxide from the atmosphere.

Biocapacity is used together with ecological footprint as a method of measuring human impact on the environment. Biocapacity and ecological footprint are tools created by the Global Footprint Network, used in sustainability studies around the world.

The Global Footprint Network was founded in 2003 and is an independent think tank originally based in the United States, Belgium and Switzerland. It was established as a charitable not-for-profit organization in each of those three countries. Its aim is to develop and promote tools for advancing sustainability, including the ecological footprint and biocapacity, which measure the amount of resources we use and how much we have. These tools aim at bringing ecological limits to the center of decision-making.

In environmental science, a population overshoots its local carrying capacity—the maximum population size that an ecosystem can sustainably support—when it exceeds the availability of resources needed for survival. This can lead to a population crash if resources are depleted faster than they can regenerate. Overshoot applies to humans as well as other animal populations: any species that relies on consumption of resources to survive.

Environmental science studies to what extent human populations through their resource consumption have risen above the sustainable use of resources. For people, "overshoot" is that portion of their demand or ecological footprint which must be eliminated to be sustainable, or the delta between a sustainable population and what we currently have. Excessive demand leading to overshoot is driven by both consumption and population.

Sustainability measurement is a set of frameworks or indicators used to measure how sustainable something is. This includes processes, products, services and businesses. Sustainability is difficult to quantify and it may even be impossible to measure as there is no fixed definition. To measure sustainability, frameworks and indicators consider environmental, social and economic domains. The metrics vary by use case and are still evolving. They include indicators, benchmarks and audits. They include sustainability standards and certification systems like Fairtrade and Organic. They also involve indices and accounting. They can include assessment, appraisal and other reporting systems. The metrics are used over a wide range of spatial and temporal scales.

For organizations, sustainability measures include corporate sustainability reporting and Triple Bottom Line accounting. For countries, they include estimates of the quality of sustainability governance or quality of life measures, or environmental assessments like the Environmental Sustainability Index and Environmental Performance Index. Some methods let us track sustainable development. These include the UN Human Development Index and ecological footprints.

The Global Hectare (GHa) is a measurement unit for the ecological footprint of people or activities and the biocapacity of the Earth or its regions. One global hectare is the world's annual amount of biological production for human use and human waste assimilation, per hectare of biologically productive land and fisheries.

It measures the production and consumption of different products. It starts with the total biological production and waste assimilation in the world, including crops, forests (both wood production and CO₂ absorption), grazing, and fishing.The total of these kinds of production, weighted by the richness of the land they use, is divided by the number of Hectares used. Biologically productive areas include cropland, forest, and fishing grounds, and do not include deserts, glaciers, and the open ocean.