Patagonian Desert albeit to the west, where precipitation is higher, bushes are replaced by grasses. Topographically the deserts consist of alternating tablelands and massifs dissected by river valleys and canyons. The more western parts of the steppe host lakes of glacial origin and grades into barren mountains or cold temperate forests along valleys. Inhabited by hunter-gatherers since Pre-Hispanic times, the desert faced migration in the 19th century of Mapuches, Chileans, Argentines, Welsh, and other European peoples, transforming it from a conflictive borderland zone to an integral part of Argentina, with cattle, sheep and horse husbandry being the primary land uses. The Patagonian
Patagonian sheep farming boom sheep-herding areas along the Strait had been leased or reserved by 1884. The sheep farming boom altered not only the demographic and economic outlook of Southern Patagonia, but also changed the steppe ecosystem. Research suggests that sheep excrement might have caused eutrophication of lagoons like Potrok Aike, and sheep might also have caused considerable erosion. The Strait of Magellan and the Atlantic coast were covered by natural grasslands so no clearing of forests occurred during the introduction of sheep. Patagonian sheep farming boom In late 19th and early 20th centuries, sheep farming expanded across the Patagonian grasslands making the southern