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 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. [1] The total of these kinds of production, weighted by the richness of the land they use, [1] 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. [2]
"Global hectares per person" refers to the amount of production and waste assimilation per person on the planet. In 2012 there were approximately 12.2 billion global hectares of production and waste assimilation, averaging 1.7 global hectares per person. [3] Consumption totaled 20.1 billion global hectares or 2.8 global hectares per person, meaning about 65% more was consumed than produced. This is possible because there are natural reserves all around the globe that function as backup food, material and energy supplies, although only for a relatively short period of time. Due to overconsumption, these reserves are being depleted at an ever increasing tempo (see Earth Overshoot Day).
The term "global hectare" was introduced in the early 2000s, [4] based on a similar concept from the 1970s named "ghost acreage". [5] Opponents and defenders of the concept have discussed its strengths and weaknesses. [6]
The global hectare is a useful measure of biocapacity as it can convert things like human dietary requirements into common units, which can show how many people a certain region on earth can sustain, assuming current technologies and agricultural methods. It can be used as a way of determining the relative carrying capacity of the earth.
Different hectares of land can provide different amounts of global hectares. For example, a hectare of lush area with high rainfall would scale higher in global hectares than would a hectare of desert.
It can also be used to show that consuming different foods may increase the earth's ability to support larger populations. To illustrate, producing meat generally requires more land and energy than what producing vegetables requires; sustaining a meat-based diet would require a less populated planet.
On average, a global hectare can be produced in the area of a standard hectare. A hectare ( /ˈhɛktɛər/ ; symbol ha) is a unit of area equal to 10,000 square metres (107,639 sq ft) (a square 100 metres on each side or 328 feet on each side), 2.471 acres, 0.01 square kilometers, 0.00386102 square miles, or one square hectometre (100 metres squared).
The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available. The carrying capacity is defined as the environment's maximal load, which in population ecology corresponds to the population equilibrium, when the number of deaths in a population equals the number of births. Carrying capacity of the environment implies that the resources extraction is not above the rate of regeneration of the resources and the wastes generated are within the assimilating capacity of the environment. The effect of carrying capacity on population dynamics is modelled with a logistic function. Carrying capacity is applied to the maximum population an environment can support in ecology, agriculture and fisheries. The term carrying capacity has been applied to a few different processes in the past before finally being applied to population limits in the 1950s. The notion of carrying capacity for humans is covered by the notion of sustainable population.
Resource depletion is the consumption of a resource faster than it can be replenished. Natural resources are commonly divided between renewable resources and non-renewable resources. The use of either of these forms of resources beyond their rate of replacement is considered to be resource depletion. The value of a resource is a direct result of its availability in nature and the cost of extracting the resource. The more a resource is depleted the more the value of the resource increases. There are several types of resource depletion, including but not limited to: mining for fossil fuels and minerals, deforestation, pollution or contamination of resources, wetland and ecosystem degradation, soil erosion, overconsumption, aquifer depletion, and the excessive or unnecessary use of resources. Resource depletion is most commonly used in reference to farming, fishing, mining, water usage, and the consumption of fossil fuels. Depletion of wildlife populations is called defaunation.
Overconsumption describes a situation where a consumer overuses their available goods and services to where they can't, or don't want to, replenish or reuse them. In microeconomics, this may be described as the point where the marginal cost of a consumer is greater than their marginal utility. The term overconsumption is quite controversial in use and does not necessarily have a single unifying definition. When used to refer to natural resources to the point where the environment is negatively affected, it is synonymous with the term overexploitation. However, when used in the broader economic sense, overconsumption can refer to all types of goods and services, including manmade ones, e.g. "the overconsumption of alcohol can lead to alcohol poisoning". Overconsumption is driven by several factors of the current global economy, including forces like consumerism, planned obsolescence, economic materialism, and other unsustainable business models and can be contrasted with sustainable consumption.
The ecological footprint measures human demand on natural capital, i.e. the quantity of nature it takes to support people and their economies. It tracks human demand on nature through an ecological accounting system. The accounts contrast the biologically productive area people use to satisfy their consumption to the biologically productive area available within a region, nation, or the world (biocapacity). Biocapacity is the productive area that can regenerate what people demand from nature. Therefore, the metric is a measure of human impact on the environment. As Ecological Footprint accounts measure to what extent human activities operate within the means of our planet, they are a central metric for sustainability.
William Rees, FRSC, is Professor Emeritus at the University of British Columbia and former director of the School of Community and Regional Planning (SCARP) at UBC.
Human overpopulation describes a concern that human populations may become too large to be sustained by their environment or resources in the long term. The topic is usually discussed in the context of world population, though it may concern individual nations, regions, and cities.
Anthropogenic metabolism, also referred to as metabolism of the anthroposphere, is a term used in industrial ecology, material flow analysis, and waste management to describe the material and energy turnover of human society. It emerges from the application of systems thinking to the industrial and other man-made activities and it is a central concept of sustainable development. In modern societies, the bulk of anthropogenic (man-made) material flows is related to one of the following activities: sanitation, transportation, habitation, and communication, which were "of little metabolic significance in prehistoric times". Global man-made stocks of steel in buildings, infrastructure, and vehicles, for example, amount to about 25 Gigatonnes, a figure that is surpassed only by construction materials such as concrete. Sustainable development is closely linked to the design of a sustainable anthropogenic metabolism, which will entail substantial changes in the energy and material turnover of the different human activities. Anthropogenic metabolism can be seen as synonymous to social or socioeconomic metabolism. It comprises both industrial metabolism and urban metabolism.
Mathis Wackernagel is a Swiss-born sustainability advocate. He is President of Global Footprint Network, an international sustainability think tank with offices in Oakland, California, and Geneva, Switzerland. The think-tank is a non-profit that focuses on developing and promoting metrics for sustainability.
This is a glossary of environmental science.
Sustainability metrics and indices are measures of sustainability, using numbers to quantify environmental, social and economic aspects of the world. There are multiple perspectives on how to measure sustainability as there is no universal standard. Intead, different disciplines and international organizations have offered measures or indicators of how to measure the concept.
In environmental science, a population "overshoots" its local carrying capacity — the capacity of the biome to feed and sustain that population — when that population has not only begun to outstrip its food supply in excess of regeneration, but actually shot past that point, setting up a potentially catastrophic crash of that feeder population once its food populations have been consumed completely. Overshoot can apply to human overpopulation as well as other animal populations: any life-form that consumes others to sustain itself.
Earth Overshoot Day (EOD) is the calculated illustrative calendar date on which humanity's resource consumption for the year exceeds Earth’s capacity to regenerate those resources that year. In 2024, it falls on August 1st. The term "overshoot" represents the level by which human population's demand overshoots the sustainable amount of biological resources regenerated on Earth. When viewed through an economic perspective, the annual Earth Overshoot Day represents the day by which the planet's annual regenerative budget is spent, and humanity enters environmental deficit spending. Earth Overshoot Day is calculated by dividing the world biocapacity, by the world ecological footprint, and multiplying by 365, the number of days in a year:
The history of environmental pollution traces human-dominated ecological systems from the earliest civilizations to the present day. This history is characterized by the increased regional success of a particular society, followed by crises that were either resolved, producing sustainability, or not, leading to decline. In early human history, the use of fire and desire for specific foods may have altered the natural composition of plant and animal communities. Between 8,000 and 12,000 years ago, agrarian communities emerged which depended largely on their environment and the creation of a "structure of permanence."
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.
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.
Land footprint is the real amount of land, wherever it is in the world, that is needed to produce a product, or used by an organisation or by a nation.
The Ten Million Club Foundation is a non-governmental organization based in the Netherlands which promotes global overpopulation awareness. For the Netherlands, it advocates to match the population size with the carrying capacity of the area. Initially, the foundation was calling for a shrinking population; later on the emphasis was also put on a reduction of the ecological footprint of the inhabitants of the Netherlands. The club was set up as a private foundation by the Dutch historian Paul Gerbrands in 1994.
The Sustainable Process Index (SPI*) was developed in the 1990s at TU Graz by a team of scientists under the leadership of professor Michael Narodoslawsky. The SPI is a member of the ecological footprint family which aggregates and compares different ecological pressures. It allows to evaluate ecologic impacts of industrial products and services like energy production, industrial products, agriculture and buildings. It provides an encompassing evaluation that distinguishes sharply between fossil and renewable energy but taking other emissions to soil water and atmosphere into account as well. Based on the idea, that the primary income of the earth is Solar radiation, in accordance with the principle of Strong sustainability the surface of the earth is the basic dimension of the evaluation. The SPI is therefore in the same family of ecological measurement as the Ecological Footprint. These methods all measure the area that is necessary to support human activities. The SPI takes the whole life cycle into consideration starting from mining of raw materials to further transformation and production of goods to recycling to disposal of waste. This includes grey emissions, the emissions which originate from production and operation of infrastructures. The SPI method is based on the comparison of natural material fluxes with technological material fluxes. The conversion of mass and energy fluxes is strongly defined by two principles of Sustainability.
Ecological overshoot is the phenomenon which occurs when the demands made on a natural ecosystem exceed its regenerative capacity. Global ecological overshoot occurs when the demands made by humanity exceed what the biosphere of Earth can provide through its capacity for renewal.
