Since at least 1959 there has been an ongoing conflict in several areas in North America between animal preservation groups and federal organizations such as The Bureau of Land Management (BLM), concerning the occurrence of wild horses and donkeys (burros) in those areas. BLM, who are the ones currently removing wild horses from their living habitats, claim that they are doing the environment and the local ecosystems a great service by capturing the horses and holding them in huge holding pens. The reason for this, according to BLM, is that the horses take a huge toll on the environment -- foremost by grazing, which is part of their natural behaviour. The BLM also claim that these wild horses are NOT a naturally occurring species in America but are an invasive species, which is why the amount of wild horses need to be controlled and in some cases completely removed for the sake of the environment. Among the animal preservation groups against this policy is The American Wild Horse Campaign (AWHC) and Return to Freedom. They question the meaning of "invasive species", by going back many thousands of years. Today's kind of horses in the US arived after 1492. But could instead look to the late Pleistocene, 13,000 years ago (Donlan et al, 2005) , when Eurasians arriving in North America began to wipe out most of the large megafauna that had shaped the continent’s ecosystems for more than 2 million years. (Perhaps the disappearance was aided by temperature fluctuations). Mammoths and mastodons disappeared and also other animals. However, species akin to today's wild horses were native to the USA and they are not to be seen as an "invasive species". Scientists have proved that the wild mustangs of today is genetically linked (via imports from Europe) to their ancestors that roamed the land. This creates an ongoing conflict where on one side the wild horse is seen as a native species that owns a right to the land and on the other side as an invasive species that needs to be controlled and removed. It is this removal of the wild horse from the land that forms the very base of this conflict. BLM acts in what they mean is the name of ecological and environmental conservation yet their opponents stress the fact that horses provides an ecological service when they get to roam freely. They also stress the fact that when wild horses and donkeys are removed from the land this is for the sake of creating spaces for other industries, such as cattle grazing/meat production and mining. These industries have profound negative environmental effects such as methane emission, deforestation and ineffective use of water and land resources.