[MUSIC] Hi learners, welcome to the seventeenth lesson of my course, ecology from south. Today, we will talk about sustainability. A resource used by human beings is defined as sustainable if it can be continued for the foreseeable future. The root of most environmental problems is the population problem, a large human population that has been growing at a more than exponential rate. Three groups of nations can be recognized, those that passed through the demographic transition early, late or not yet. Even if were possible instantaneously to bring about the transition in all remaining countries of the world, the population problem will not be solved partially because population grow as it's momentum. The global carrying capacity for human beings is variously estimated at between one and 1000 million, depending mainly on what is deemed to constitute an acceptable standard of living. Whenever a natural population is exploited by harvesting, there is a risk of over-exploitation. But harvesters also want to avoid under-exploitation when potential consumers are deprived of resources. The concept of the maximum sustainable yield, MSY, has been a guiding principle in the exploitation of natural populations. There are two simple ways of obtaining an MSY on a regular basis, through a fixed portal or through a fixed effort. Two limitations of the MSY approach are that it treats all individuals in the population as identical and that it treats the environment as unvarying. Improved harvesting strategies correct both these oversights. Lack of knowledge of most fisheries around the world means that management is often based on the precautionary principle, often in the absence of data. Increasingly, animals and plants have been domesticated and managed in a way that allowed much larger harvests, usually as mono-cultures. But a high price may be paid to maintain this high rate of food production. Monocultures offer ideal conditions for the epidemic spread of disease and lead to widespread degradation of land. In an ideal sustainable world, new soil would be formed as fast as the old was lost. But in most agricultural systems, this is not achieved. When there is an overwhelming reliance on artificial fertilizers, maintaining the organic matter capital of the soil tend to be neglected, and this has declined worldwide. Soil degradation can be slowed down by incorporating manual alternating cultivation and fallow periods, or returning the land to grassy pasture. In tropical regions, cultivation is more difficult because most of the nutrients are in the biomass and not in the soil. In other regions, instead, overgrazing and excessive cultivation can lead to desertification and salinization. Water is widely told to be the resource that future wars will be fought over. On a global scale, agriculture is the largest consumer of fresh water. And pumping fresh water from underground aquifers is the main cause of loss of the agricultural land through salinization. The aim of pest control is to reduce the pest population to its economic but the so-called economic threshold may be of more immediate importance. Pesticide makes the species harder than they target, and may give rise to target faster solutions or secondary pest outbreaks. Pests may also evolve pesticide resistance. Biologists may also manipulate the natural enemies of pests in a way that is called biological control via three forms of biological control. That is incorporation, conservation, or inoculation, but even biocontrol agents can have unwanted effects on nontarget species. Integrated pest management, IPM, is a practical philosophy of pest management that is ecologically based that uses all means of control where appropriate. It relies heavily on natural mortality factors, and it calls for specialist pest managers or advisors. Evidence has been accumulating that the organic production as a sustainable farming approach can yield economic returns too. It is clear that very significant threats are posed to ecosystems around the world by the increasing human population and concomitant increases to agricultural development. These are expected to have a particular damaging effect on biodiversity, because most agricultural growth is predicted to occur in the species-rich tropics. The production of coffee, chocolate, tea, palm oil, and other tropical foods is considered one of the main causes of tropical deforestation. So at the end of this lesson, I have some questions for you. What is sustainability? Then, is it possible to have sustainable population growth? Next question, is it possible to have sustainable use of fossil fuels? Or is it possible to have sustainable use of forest trees? So, please try to answer this question, and see you in next lecture. [MUSIC]
