Sustainability is the ability to perform an activity or use a resource, such as an energy source, a raw material, a species or a habitat, for a prolonged period, such as centuries or millennia, and without any major harmful effects.
Some sustainable resources are available in perpetuity without any fear of depletion, such as sunlight and wind. However, many of the most essential resources for humans are not sustainable at current rates of consumption. Moreover, their sustainability is continuously decreasing because of growing population and new or expanding applications. The only way to survive this impending catastrophic situation is the implementation of strict resource conservation policies, a key component of which would be demand reduction.
One of the most fundamental resources, fresh water, while itself a renewable resource, is not sustainable at current rates of consumption because of pollution of water sources, groundwater depletion, loss of wetlands, and climate change. Soil is likewise not sustainable at current rates of use, largely because of farming practices which result in its degradation and erosion and also because of conversion of farmland to other uses and climate change. Phosphate rock, the primary source of phosphorus, which is essential for the synthetic fertilizer necessary for high crop yields, is similarly being rapidly depleted.
Estimates for the availability of coal, still one of the top sources for producing electricity, range up to in excess of four hundred years at current rates of consumption. However, this fossil fuel is clearly not sustainable because of its ever-increasing damage to both the environment and public health. Petroleum and natural gas likewise are not sustainable, not only because of their harmful environmental effects, but also because their reserves are measured only in decades, not centuries.
Nuclear fission cannot be considered a sustainable energy source because of the vast and ever-growing amount of radioactive waste that is accumulating and for which no truly safe and economical disposal solution has been found. It can also be considered unsustainable because of the extensive environmental damage that inevitably results from uranium mining. Nuclear fusion, on the other hand, may become a more sustainable energy source than nuclear fission because of the lower volume and shorter half life of its radioactive waste as compared to fission, although large scale availability is not likely for at least two decades or more.
Plant-based resources, including food crops and industrial crops, can be highly sustainable because of their ability to regenerate and their typically beneficial effects on the environment, such as carbon sequestration, providing habitat, and soil enrichment. However, they often require extensive management, depending on the species, including planting, providing water and nutrients, and limiting consumption. Examples of particularly sustainable plant-based resources include bamboo and seaweed, which can easily regenerate in a wide range of conditions require little if any human intervention.