Natural features that provide a capacity to do work through combustion, movement, radiation, or heat; these resources include oil, natural gas, coal, wind, sun, currents, tides, and natural heat gradients. Distributions are recorded observations, maps, or models of specified resources at known locations, in some cases as a function of season or other temporal scales. Assessments are evaluations of the economic or ecological value associated with the resources or of the difficulty, environmental effects, or sustainability of energy extraction and production. Some assessments can appropriately be included in the Energy Resources category and also in related Living Resources or Uses categories. Predictions are the results of models or projections of future distributions, values, or impacts of energy resources; these data include forecasts of changes due to natural and human processes, such as resource losses or gains under different rates of resource extraction, effects of climate change, and so on.