TOPIC:- How do human activities alter the flow of energy and cycling of key nutrients through ecosystem?
Dynamics of energy flow and the transport of matter in hydrological and biogeochemical cycles have evolved over millions of years into complex, finely tuned systems. As humans began to inhabit parts of Earth, initially the environmental impacts of their activities were very localized and had little influence on global processes. In the recent past, human populations have grown tremendously, spreading out over land areas. Research now indicates that the influence of human activity on energy flow and biogeochemical cycling can lead to significant changes in global climate and primary productivity.
Talking of nutrients–essentially chemical elements,are first taken up by plants, which are consumed by humans or animals, and excreted again by them — or they are released back into the environment when organisms die (e.g. plants lose their leaves).Microorganisms in the soil break this matter down,and again make nutrients available in their mineral form,which makes it possible for plants to take them up again. As described above, nutrients are continuously recycled in are continuously recycled in a natural ecosystem.
In recent decades, population growth and resulting human activities such as large-scale farming have caused some significant changes in nutrient cycles.With harvesting crops, nutrients are removed from the soil. For centuries, dung from animals has been used as a fertiliser to restore the nutrients back to the soil, and in many cultures – e.g. in Europe, or also in China, also human excreta have been recycled back to agricultural fields. Hence, nutrients went back into the soil at roughly the rate they had been withdrawn. However, with the introduction of water-borne sewage, this cycle was interrupted and replaced by a linear system that transports nutrients away from soils and into watercourses....