Sustainable yield
The sustainable yield is a form of sustainability that refers to the maximum harvest that does not deplete or over-harvest where the renewable resource can not grow back. In the simplest terms, sustainable yield is the largest amount of resource that humans can take or use without causing damage or allowing for a decline to happen in the specific population. In more formal terms, the sustainable yield of natural capital is the ecological yield that can be extracted without reducing the base of capital itself, i.e. the surplus required to maintain ecosystem services at the same or increasing level over time. The term only refers to resources that are renewable in nature as extracting non-renewable resources will always diminish the natural capital. The sustainable yield of a given resource will generally vary over time with the ecosystem's needs to maintain itself, e.g. a forest that has recently suffered a blight or flooding or fire will require more of its own ecological yield to sustain and re-establish a mature forest. While doing so, the sustainable yield may be much less. The term sustainable yield is most commonly used in forestry, fisheries, and groundwater applications. A sustainable yield is calculated by the carrying capacity divided by 2. At half of the carrying capacity, the population can be harvested and quickly recover, allowing for more resources. Although this calculation seems easy, it is not because it is difficult to calculate the carrying capacity of a population in nature since it is almost always based on estimations. Understanding sustainable yield is essential to nature since it indicates how much a population can produce and what humans can glean from without causing fundamental problems in the specie's population. If the population is harvested above its maximum sustainable yield, it can eventually risk extinction. Sustainable yield is an important component of sustainable forest management. In the forestry context it is the largest amount of harvest activity that can occur without degrading the productivity of the stock.