Carrying Capacity

Carrying capacity is a quantitative measure of the human, animal, or vegetative population that a specific environmental space can support. It may be calculated for various scales, from the local to the global. It is an important concept in cultural ecology and environmental studies, is a centerpiece of the notion of sustainable development, and is derived from Malthusian Theory. Carrying capacity represents equilibrium between a population and its environment: A population that is below the carrying capacity of its environment will in theory increase to the number represented by the carrying capacity, while a population that is above the threshold of the carrying capacity will die back to that level.

Carrying capacity is a dynamic concept and may be affected by many different factors. In the case of a human population, the carrying capacity of some regions may change dramatically in a short period due to changes in technology or variation in local climate. The carrying capacity of a certain hectare in Africa’s Sahel region, for example, may be ten adults under current conditions. This means that enough food can be produced using current technology and under current climatic conditions to support ten grown people. But, if the following year is particularly dry and a drought occurs, the carrying capacity for that year may drop to seven, meaning that famine will likely be prevalent in the region. On the other hand, if climatic conditions are good and the farmers working the hectare are presented with a tractor, an improved hybrid that is more productive or more resistant to insect damage, or some other technological innovation, this change will suddenly increase the carrying capacity. For example, the carrying capacity of some farmland in India, the Philippines, and other developing areas dramatically rose between the mid-1960s and the early 1990s from the technological success of the Green Revolution, as yields per acre in some areas increased by a factor of three. In some areas of south Asia yields for wheat doubled in only five years.

On the other hand, the carrying capacity of much of the Sahel has declined during the same period, due to overgrazing, drought, and soil erosion. Carrying capacity for nonhuman species, an important concept in wildlife management and ecology, tends to be more stable because such species do not introduce technological innovations that alter the food-producing capacity, although changes in the environment can affect the carrying capacity.