Now that you have an idea of how water cycles through ecosystems, in this module you’ll learn about climate and weather, which will dictate much about how water relates to the agroecosystem of your specific region. The work of any agoecologist is to intimately get to know the patterns of their region so they can work with the natural rhythms of the area. Of course, these patterns have begun to shift dramatically due to climate change making predicting and preparing for climate and weather changes difficult though evermore necessary.
Climate: annual average conditions
Weather: climatic conditions at one moment in time
Average Annual Rainfall: The mean quantity of rain that occurs in a place over a one-year period.
Average Annual Precipitation: The mean quantity of precipitation (including drizzle, rain, sleet, snow, graupel and hail) in a place over a one-year period.
Describing Rainfall Patterns
It is important to understand the precipitation patterns in an ecosystem in order to understand the opportunities for and the constraints upon agriculture in a particular region. Bellow you will see some of the main criteria used to describe a rainfall pattern:
Average Total Annual Precipitation
While the total amount of precipitation that falls in an area during an average year is a good indicator of moisture availability, this number alone isn’t enough. It’s important to know how much variability there can be in the average total rainfall amount year-to-year. Extremes can have a serious effect on an agricultural systems, even if the extreme only occurs rarely.
Distribution and periodicity
How rainfall is spread throughout the year, both on average and during a specific year. In many areas, there are predictable wet and dry periods during the year. One example of this is the Mediterranean climate, in which ecosystems experience wet winters and have long dry spells during the summer.
Different factors affect how rainfall becomes available as soil moisture. Does it penetrate into the root zone? Does it fall with a serious intensity (such as many inches of rain in a short time period) and lead to runoff and flooding?
The degree of variability in rainfall patterns. The higher the variability, the less predictable the rainfall for any particular time period is.
Each organism, plants and animals both included, has certain limits of tolerance for high and low temperatures, determined by its particular adaptations for temperature extremes. Each organism also has an optimum temperature range, which can vary depending on the stage of development. The temperature range and degree of temperature fluctuation in an area can set limits on the crop species and cultivars a farmer can grow. For example, because of their different reactions to temperature, papayas are not planted in the cool coastal temperate environment of the Monterey Bay California, and apples would not do well if planted in the humid tropical lowlands of Mexico. Temperature has a huge effect on regional cuisine. It is necessary to consider the temperature when selection crops appropriate to the climate of the agroecosystem.
Determining the Climate and Rainfall Patterns of Your Ecosystem
Take a look at the maps below and consider the average rainfall and temperature of the ecosystem you are in. How might that effect your agroecosystem?
From Gliessman, Stephen R. Agroecology: The Ecology of Sustainable Food Systems. 2nd ed. Boca Raton: CRC Press, 2007.