5.11 Ecological Footprints

An ecological footprint is the area of biologically productive land and water needed to produce the resources a person, city or country consumes and to absorb its wastes, especially its carbon dioxide. It includes cropland for food, pasture for meat and dairy, forests for wood and paper, fishing grounds for seafood, land covered by buildings and roads, and forest area needed to absorb CO₂ emissions.

Footprints are usually measured in global hectares (gha), a standard unit representing a hectare of land with world-average productivity. This lets scientists compare different kinds of land fairly.

Biocapacity is the amount of productive area actually available. When a population's footprint is larger than its biocapacity, it's using resources faster than nature can regenerate them.

Footprints depend mainly on consumption, which rises with wealth. People in high-income countries like the U.S. tend to have footprints several times larger than the world average, because they eat more meat, live in larger homes, drive and fly more and buy more goods. People in low-income countries have much smaller footprints.

Globally, the Global Footprint Network estimates that humanity uses resources as if we had about 1.7 Earths. That's possible only for a while, by depleting resources like fish stocks, forests and groundwater and by letting CO₂ build up in the atmosphere.

A carbon footprint is the total amount of greenhouse gases emitted by a person's or organization's activities, usually expressed in tons of CO₂ equivalent. It includes direct emissions, like burning gasoline in a car, and indirect ones, like the emissions from producing food, electricity and products you buy. The carbon footprint is the largest single part of humanity's total ecological footprint, roughly 60%, and of most wealthy countries' footprints, but the ecological footprint also counts land for food, wood and buildings.

Total impact depends on three things: how many people there are, how much each person consumes, and how damaging the technology used to meet that consumption is. Changing any of them changes the footprint.

• Eat less meat, especially beef, and waste less food.
• Use public transit, walk, bike or carpool, and fly less.
• Use energy-efficient appliances, insulate homes and switch to renewable electricity.
• Buy fewer, longer-lasting products, and reuse and recycle.
• At larger scales, build denser cities, protect productive land and improve technology.