The Savory brittleness scale is used to describe the annual distribution of humidity in a particular environment. It was developed by Allan Savory

Allan Savory

Allan Redin Savory is a Zimbabwean biologist, farmer, soldier, exile, environmentalist and winner of the Banksia International Award 2003. and winner of the Buckminster Fuller Award 2010...

, a Zimbabwe

Zimbabwe

Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

an biologist. The scale is used in land management because the distribution of humidity affects the way that land, particularly when degraded, responds to being rested. Most commonly the scale is used to guide the use of cattle or other herding animals in the maintenance and restoration of land which is brittle or subject experiencing desertification.

Scale

The scale ranges from 1 to 10 with 1 being non-brittle and 10 being very brittle. The scale is not precise and is a matter of judgment rather than applying a formula. A tropical rainforest

Tropical rainforest

A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

 would measure 1 on the scale, and an arid desert

Desert

A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...

 such as the Sahara

Sahara

The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...

 would rate a 10.

The scale reflects the distribution of humidity throughout the year, not the amount of rainfall. For this reason, it differs from an aridity index

Aridity index

An aridity index is a numerical indicator of the degree of dryness of the climate at a given location. A number of aridity indices have been proposed ; these indicators serve to identify, locate or delimit regions that suffer from a deficit of available water, a condition that can severely affect...

. Thus, some high rainfall environments, e.g., Zambia, with 2,000 mm annual rainfall and distinct wet and dry seasons, can be high on the brittleness scale because of the long portions of the year without rainfall. An environment with lower total rainfall distributed fairly evenly throughout the year, such as parts of England with 600 mm annually, can be low on the brittleness scale.

Effect of Brittleness

While total rainfall is important for understanding the ability of an area to be productive during the growing season, brittleness gives an indication of the ability of insects and bacteria to degrade dead plant material throughout the year. A brittle environment may be characterized by grasses which grew during the rainy season and which died during periods of extended dryness and are still standing at the time the rains return. This lack of decay means the dead grasses shade new plant growth, reducing the productivity of the area during the rainy season.

Non-brittle lands, such as rain forests, will not remain empty of plant life for long periods of time if they are cleared and fully rested. Continuous availability of moisture promotes a continuous cycle of the growth of new plants, and upon their death, their decomposition so space is made for following generations.

At the other end of the scale are brittle and very brittle lands. If left rested after being cleared these lands often do not recover.

Application to Land Management

Brittle landscapes have erratic distribution of moisture throughout the year. The main significance of this scale is that the "tool" of resting land in either form - total rest or partial rest - leads to grasslands weakening and being replaced by either woody vegetation or bare soil covered with algae and lichens depending on the amount of rainfall. Partial rest, a new concept named by Savory, describes situations in which there are large herbivores on the land who are scattered and exhibit calm unbunching behavior. Research plots across the brittleness scale indicate that the effects of partial and total rest are almost identical in grasslands and savannas. Partial rest in high end brittle environments, particularly where combined with overgrazing of plants, is the single greatest influence leading to desertification

Desertification

Desertification is the degradation of land in drylands. Caused by a variety of factors, such as climate change and human activities, desertification is one of the most significant global environmental problems.-Definitions:...

.