Other common fowl include gray hawks, partridges, martins, coots and storks. The region is also home to pumas, pampas foxes, cavias, maras and other drought-resistant mammals, as well as some also common to North America, like skunks and opossums. The arrival of British-financed railways to the region in the 1880s brought with it the area's first significant presence of white settlers, some of whom had served in the regiments involved in the Conquest of the Desert and were granted vast tracts of land. Much of the area was subsequently fenced into cattle and sheep ranches, which dominate the region's land use to the present day; area ranchers raise approximately four million cattle (a tenth of Argentina's). Since the 1940s, advances in agriculture and crop breeding have allowed for intensive wheat, sunflower, oats and alfalfa cultivation, as well. Though many of the hydroelectric projects put into place since then have encouraged the development of a scattering of prosperous urban areas like Santa Rosa, La Pampa, some have had unintended consequences to the area's ecological balance. Dams along the Atuel River, for instance, are often allowed to release the rainy season's excess water with little regard to the area around rural Algarrobo del Aguila, La Pampa, causing avoidable inconvenience and disruption of nearby wetlands. Until recently, the region was the only one in Argentina lacking a national park or natural preserve. In 1971, descendants of La Pampa Province landowners Arminda Roca and Pedro Luro deeded 7,600 hectares (29 mi2) to the provincial government, which opened the park to the public five years later. Though the area would not be designated as fully protected until 1996, this was the first significant move to protect the biome. Today the Luro Park Natural Preserve is the most visited such area in the dry pampas region. In 1977, a 9,900 hectare (38 mi2) parcel in La Pampa Province's southern dry grasslands were set aside as Lihué Calel National Park. These accomplishments notwithstanding, the area's ecosystem has been under increasing pressure by grazing and irrigation activities, apart from population and economic growth themselves.