Hoofprints on the Land by Ilse Köhler-Rollefson

Author:Ilse Köhler-Rollefson
Language: eng
Format: epub
Publisher: Chelsea Green Publishing

Research on Spain’s transhumant sheep revealed that the Cañadas represent ecological corridors that facilitate the movements of plants and insects and that livestock act as ‘seed taxis’. This phenomenon was first studied in depth by Pablo Manzano and Juan Malo who discovered that a flock of a thousand sheep can transport 200 million seeds during their 1,500km (900 mile)-long migration. In times of climate change, this is of phenomenal importance. It allows plants to move from a habitat they were originally adapted to but that has become too hot or dry, or otherwise hostile, into a new area that provides better conditions. Sheep act as a removals van for plants to an environment that is more to their liking, and this works not only for plants, but also for lizards, beetles and grasshoppers. Their service thereby prevents extinction due to climate change as it can be an important vehicle for plants to move into new areas that fit their requirements and thereby prevent their extinction.12 In Germany, scientists have tried to put a price tag on the ecological services provided by sheep, who were found to redistribute up to 8,500 seeds from 57 species, and came up with the value of some 4,500 euros for a 200-head flock, if the seeds had to be purchased, transported and sown.13

Sheep don’t just do this by default due to the nature of their wooliness; some herders make conscious efforts to disperse the seeds of preferred plants. An example for traditional regeneration is provided by pastoralists in the Islamic Republic of Iran who pack seeds in little bags and hang these around the necks of their sheep. During grazing the seeds drop through little holes in the bags and are worked into the ground by the sheep’s hooves.14

It is not just that livestock transport seeds, they also aid their germination through scarification. ‘Scarification’ is a botanical term that refers to weakening the coat of a seed, so that it can break up and germinate. Many acacia trees, for instance, have very hard seed coats and their seeds need to pass through the stomach of a ruminant in order to sprout. The rescued camels that we kept in an enclosure on our campus for several months about five years ago left us a lovely gift: they have turned what was a bare field into a fledgling forest of young acacia (Acacia leucophloea) trees, a species that is otherwise difficult to propagate.

After they have scarified the seeds, livestock then conveniently trample them into the ground like a forest gardener. Trampling has other ecological effects as well, mostly positive, although it all depends on the intensity and the context. The depressions left by hooves can become filled with water and turn into mini habitats for insects and amphibians, which then provide food for all kinds of birds and mammals. And here we come to the general role of grazing animals at the bottom of the food chain. Their droppings are powerful incubators for a huge diversity of

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