Useful concepts

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Ideas that are widely respected and useful for understanding sustainable development

The Tragedy of the Commons and carrying capacity [Sources: Allaby p57 and IUCN p10]

Garret Hardin wrote the article with the above title and helped to clarify the meaning of 'carrying capacity'. He reasoned that cattle farmers all wish to increase the size of their herds. This is fine until the total number of cattle approach the limit that can be grazed satisfactorily on a particular 'commons'. It is still profitable for each individual farmer to increase his herd even though the carrying capacity is being exceeded and the total output starts to drop. If the commons can support 100 cows and 20 farmers each own 5, then each farmer who adds one cow to his herd gains 20%, but looses only 1% in terms of overall damage. If each farmer thinks like this and acts accordingly then in due course they all suffer. The principle of unregulated markets states that every farmer should increase his herd until the loss exceeds the gain - by which time all the cattle will be very scraggy.

The 'tragedy of the commons' is being enacted in numerous ways today. Consider for example over-fishing of the oceans, over-use of popular recreation sites, tropical forests, clean water resources and the growing use of private cars. We are living beyond the Earth's carrying capacity as is demonstrated in Beyond the Limits, the sequel to Limits to Growth. However, recognising this fact may encourage us all to strive for a sustainable future.

There are finite limits to the Earth's carrying capacity - the impacts that the biosphere can withstand without serious deterioration. the carrying capacity varies from region to region and the impacts depend on the number of people, the amount of food, water, energy and raw materials being used and the amount of waste being generated. A few people consuming a lot can have an impact equivalent to a lot of people consuming little. With care and appropriate attention the carrying capacity can improve as well as deteriorate, but current trends reveal few, if any examples, where steady improvement is taking place.

Our Ecological Footprint [Source: Wackernagel]

"Ecological footprint" analysis provides a planning tool that can help us to work towards a sustainable future. "The Ecological Footprint is a measure of the 'load' imposed by a given population on nature. It represents the land area necessary to sustain current levels of resource consumption and waste discharge by that population." For example, The Netherlands population is 15 million people (4.4 people per hectare) and they require 15 times the land available in their own country to support their lifestyles. Similarly Londoners require a land area equivalent to most of the British Isles to sustain their lifestyles.

Every country cannot have an ecological footprint that exceeds its land area. In general wealthy people can afford to live where the ecological footprint exceeds the available land surface, by relying on poorer countries for many of their resource requirements.

Natural Capitalism [Source: Hawken et al]

Natural capital is created by the complex interaction of thousands of organisms, insects and species. For example soil fertility is achieved by countless organisms, some of which are not understood and others remain unknown, and yet we rely on their complex interactions for the nutrient flows that enable us to grow crops, trees etc. In addition to its fertility, soil stores water, decomposes waste, removes litter, transforms animal matter, and cleanses toxins.

Unlike human capital, natural capital cannot be produced by human activity. It is easy to take natural capital for granted, like fish take the water in which they swim for granted. It is easy to live our lives without giving any thought to the sulphur cycle, wetland functions, or how tiny organisms reproduce. We take action only when there has been some dramatic disruption of an ecological system.

The time has come to recognise that 'productivity' now needs to be measured in terms of our use of nature. When people were the scarce resource it was appropriate to measure their productivity, now natural capital is our scarce resource and it's time to consider how to use it.

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Last modified 17 November