Produced by sun energy, i.e., RMR of plant origin.

The third important characteristic of RMR is that they are renewable. "Renewable" can be described as "being part of a relatively short ecosystem cycle", i.e. cycle which acts on a human or biological time scale. But we should stress here that renewability is just a potentiality; the theoretical potentiality to be renewed into exactly the same form in the same place. Therefore, actual renewal is conditional in the sense that it depends on (human) influences upon ecosystems. Over exploitation will lead to exhaustion or extinction of RMR. One also can talk about partial renewal, i.e., renewal in terms of the carbon cycle, but not in terms of nutrient cycles. Here again renewal can be realized by the human intervention as in the case of use of fertilizers, the tissue culture or genetic engineering! Therefore, it may be necessary to differentiate between "natural renewal" and "cultural renewal". Natural renewal occurs within totally natural ecocycles without leading to their disturbance, i.e. preserving the resilience of the ecosystem, which is unsubstitutable. Therefore, proceeding from the precautionary principle including a sound sceptism regarding human intervention in nature: the natural renewal of RMR should be given a high priority as compared with cultural renewal. This gives a productive meaning to the concept of natural capital which means that the preservation of the ecosystems is the guarantee of actual renewal of RMR, and hence their sustainable availability.