The brittleness scale is explained by the second of Allan Savory’s key discoveries: environments can be represented on different ends of a scale depending on the degree that moisture is available to growing plants, how well humidity is distributed throughout the year, and how quickly dead vegetation breaks down. All environments appear at some point along this scale. Acknowledging that an action can produce different results in contrasting environments is just as obvious as it is important.

Second Key Insight: Environments must be identified on a scale of how much moisture they receive throughout the year

One end of this scale contain the non-brittle tending environments that have reliable moisture regardless of quantity throughout the year. Humidity here is distributed throughout the year and dead vegetation breaks down rapidly, on a microscopic, biological level compared with brittle environments, without the need of disturbance. Smaller, solitary herbivores and predators inhabit these pristine environments.

At the opposing end of the scale are brittle tending environments in which precipitation and humidity are seasonal and erratic and scattered irregularly throughout the year regardless of quantity. Dead vegetation tends to break down slowly in brittle environments through chemical decomposition. Without the presence of large herbivores providing adequate disturbance, soil-building biological decomposition is minimal. In once pristine environments this disturbance was provided by herds of wild herbivores, moving through the landscape in response to migration patterns and the presence of pack-hunting predators. Specific animal behavior tied to these events is key in order for there to be the necessary vegetation and soil surface disturbance.

Brittleness is measured on a scale from 1 to 10, 1 being non-brittle and 10 being very brittle, as represented in the diagram below. The brittleness scale is about the evenness of the spread of humidity in the atmosphere over the course of a year. It is not about the quantity of precipitation that falls but the constancy of humidity at the soil surface. If you have periods of the year when it is very dry, and it does not rain for a prolonged period of time, and you then follow that with a wet season then you have seasonality in precipitation. It is a brittle-tending environment. When it is raining or is likely to rain in every month, there is little seasonality, and you are non-brittle tending. The more seasonal, the more pronounced the dry period is and the wet period is, the more brittle tending your location is.