Humans are part of ecosystems, not separate from them. We depend on nature for food, water, clean air and a stable climate, and our activities now shape almost every ecosystem on Earth. Human ecology studies these relationships. This module looks at what nature provides, how we measure our demand on it, and how that demand can be reduced.
What you will learn
- The four categories of ecosystem services, with examples
- How the ecological footprint and biocapacity are calculated
- What Earth Overshoot Day and planetary boundaries mean
- How footprints vary between countries and lifestyles
- Practical ways to reduce your footprint, including as a traveller
Ecosystem services
Ecosystem services are the benefits people obtain from nature. The Millennium Ecosystem Assessment (2005) grouped them into four categories:
| Category | What it means | Examples |
|---|---|---|
| Provisioning | Products we take from nature | Food, fresh water, timber, fibre, medicines, fish |
| Regulating | Natural processes that keep conditions stable | Pollination, climate regulation, flood control, water purification, pest control |
| Cultural | Non-material benefits | Recreation, tourism, spiritual value, inspiration, education |
| Supporting | Underlying processes that make other services possible | Soil formation, nutrient cycling, primary production |
Today the concept is often described as nature’s contributions to people, which recognises that different cultures value nature in different ways.
Some examples of the scale of these services:
- Pollination by insects and other animals supports crops worth hundreds of billions of dollars a year.
- Mangroves reduce storm surges and protect coastal communities; their loss has increased damage from cyclones and tsunamis.
- Wetlands filter pollutants. New York City chose to protect the forests of the Catskill Mountains to keep its drinking water clean instead of building an expensive filtration plant.
- Wildlife tourism is a major source of income for countries such as Kenya, Tanzania, Botswana, Rwanda, Costa Rica and Nepal.
The ecological footprint
The ecological footprint, developed in the early 1990s by Mathis Wackernagel and William Rees, measures how much biologically productive land and sea area is needed to provide the resources a person, city or country uses and to absorb its waste, especially carbon dioxide.
It is compared with biocapacity: the area of productive land and sea actually available. Both are measured in global hectares (gha), standardised units of average productivity.
The footprint combines six types of demand:
- Cropland for food and fibre.
- Grazing land for livestock.
- Fishing grounds.
- Forest for timber and paper.
- Built-up land for housing and infrastructure.
- Carbon footprint: the forest area needed to absorb CO₂ emissions from fossil fuels. This is the largest component for most countries, around 60 percent of humanity’s total footprint.
Overshoot
According to the Global Footprint Network, humanity currently uses resources about 1.7 times faster than Earth’s ecosystems can regenerate them. In other words, we would need about 1.7 Earths to sustain current demand. This is called ecological overshoot. It is possible only by depleting stocks: overfishing, cutting forests faster than they regrow and accumulating CO₂ in the atmosphere.
Earth Overshoot Day marks the date each year when humanity’s demand exceeds what Earth can regenerate in that year. In recent years it has fallen around late July or early August.
Footprints differ enormously between countries. The average person in the United States, Canada, Australia or the Gulf states has a footprint several times larger than the global biocapacity per person, while the average person in many countries in Africa and South Asia has a footprint well below it.
Planetary boundaries
In 2009 a group of scientists led by Johan Rockström proposed nine planetary boundaries: limits for processes that regulate the stability of the Earth system, within which humanity can operate safely. They include climate change, biosphere integrity (biodiversity loss), land-system change, freshwater use, nitrogen and phosphorus flows, ocean acidification, atmospheric aerosols, ozone depletion and novel entities such as plastics and synthetic chemicals. A 2023 update concluded that six of the nine boundaries have been crossed.
Criticisms and limits of the footprint
The ecological footprint is a powerful communication tool, but it has limits:
- It does not directly measure biodiversity loss, pollution such as pesticides, or water use.
- Converting everything into land area involves assumptions, especially for carbon.
- National averages hide large differences between rich and poor people within countries.
It is best used alongside other indicators, such as the carbon footprint, water footprint and biodiversity footprint.
Travel and your footprint
Travel, especially flying, can be a large part of an individual’s footprint. A single long-haul return flight can generate one to several tonnes of CO₂ per passenger, comparable to months of emissions for an average person worldwide. That does not mean wildlife tourism is bad: well-managed tourism funds conservation, creates jobs and gives local communities a reason to protect wildlife. It means choosing carefully:
- Fly less, stay longer. One longer trip has a smaller footprint than several short ones.
- Choose operators that support conservation and local communities, such as lodges in community conservancies.
- Follow wildlife viewing rules: keep your distance, limit vehicles at sightings and never feed wild animals.
- Avoid wildlife exploitation, such as riding elephants, walking with captive lions or buying wildlife products.
- Travel overland where possible, and consider contributing to verified conservation or restoration projects.
See our Safari & Travel guides for responsible choices at each destination.
Case study: Costa Rica
In the 1980s, Costa Rica had one of the highest deforestation rates in the world, with forest cover falling to around a quarter of its land. The country introduced payments for ecosystem services, paying landowners to protect forest, protect watersheds and store carbon, funded partly by a fuel tax. Combined with a network of national parks and a booming ecotourism industry, forest cover has recovered to over half the country. Costa Rica shows how valuing ecosystem services can reverse habitat loss while supporting the economy.
Try it yourself
Use a free online ecological footprint calculator, such as the one provided by the Global Footprint Network. How many Earths would be needed if everyone lived like you? Which category contributes most? Choose two realistic changes and recalculate.
Common misconceptions
- “Nature’s services are free, so they have no value.” They are free to use but extremely costly to replace.
- “Population alone explains our footprint.” Consumption per person matters as much as population size.
- “Tourism always harms wildlife.” Poorly managed tourism can; well-managed tourism is one of conservation’s most important sources of funding.
Key terms
- Ecosystem services: benefits people obtain from nature.
- Ecological footprint: the productive area needed to support consumption and absorb waste.
- Biocapacity: the productive area available.
- Global hectare: a hectare of average biological productivity.
- Overshoot: when demand exceeds biocapacity.
- Planetary boundaries: safe limits for Earth-system processes.
Quick quiz
Test what you have learned. Scoring 60 percent or more marks this module as complete.
Further reading
- Wackernagel, M. and Rees, W. (1996). Our Ecological Footprint.
- Richardson, K. et al. (2023). “Earth beyond six of nine planetary boundaries.” Science Advances.