At a smaller scale, other scientists may investigate the processes involved in cycling water and the elements of life through the biosphere: carbon, nitrogen, sulfur, phosphorous, and other elements. These studies can also provide "ground-truth" - observations on the ground which are used to validate the remotely sensed data. As more and more observational and experimental data become available, other scientists construct models to help us understand the biosphere, how it evolved, and even provide tools that allow for predicting the future response of the biosphere to global change and human activities.
