What is meant by “Carrying Capacity?"
Increasing concern about deer-related problems indicates that deer populations in some areas of Connecticut, notably Fairfield County, have exceeded an optimum density called the carrying capacity. Carrying capacity can be determined by three different standards, each representing a different stage or level of deer population:
A) Cultural carrying capacity is reached when the deer population is high enough to cause widespread conflict with the nearby human population. The deer are thriving and typically have twin fawns. If nothing is done to stabilize or reduce the deer population, conflicts increase with both citizens and deer suffering as a result.
B) Ecological carrying capacity is that deer density at which we see damage to the forest ecosystem, impacting the populations of plants and other wildlife species, forest regeneration and water quality. The deer remain healthy and typically have twin fawns. To prevent irreversible losses of woodland plant and small animal species, deer populations must be reduced at this stage.
C) Biological carrying capacity is the population density that cannot be supported by the available habitat. The forest is devastated and little food remains. Catastrophic mortality, from such causes as starvation, stress, diseases and parasites, and reproductive failure, produce a dramatic decline in the population and poor health in the surviving individuals.
In Fairfield County, the cultural and ecological carrying capacities have apparently been exceeded, but we have not yet arrived at the biological carrying capacity on a widespread basis. This means that the deer remain healthy but the forest does not. The woodlands are unable to recover each year from the degree of overbrowsing by deer and gradually decline while the deer population continues to grow. We have not yet reached the stage when hunting deer would cause a rebound recovery of the deer population, as the deer are not yet stressed to that extent and their reproduction remains high. At the current levels of deer and of woodland damage, a deer culling program would reduce the deer population (assuming enough deer were removed annually to keep ahead of their reproduction rate) and allow woodland recovery before it is too late for the ecological integrity of our natural spaces.