Most studies are limited to major crops, and the effects of climate change on many other important crops are much less known. There is evidence that climate change has already negatively affected wheat and maize yields. These include: physical ones, such as temperature, precipitation patterns and COj fertilization; changes in agroecosystems (e.g. through loss of pollinators and increased incidence of pest and diseases); and the adaptive responses of human systems. Effects of temperature changes are generally well understood up to the optimum temperature for crop development; however, beyond these optimum temperatures, effects are much less known.