Horse hooves are hard and when they impact the ground, they crush vital plants and compact it so if the area gets rain, the water isn’t absorbed into the ground and just runs-off. As Australia is the driest inhabited continent on earth with very limited rainfall, this is a very serious problem especially in areas where feral horses are found.
They occupy valuable farming land and when that land is being used, they go in and eat the crops and plantations, and if there are cattle, they graze in the paddock that has been set aside for cattle grazing, so there is nothing left for the cattle when they are moved into that grazing paddock.
If fences are put up around paddocks the horses break them down, being the strong animals they are. This is a very serious problem, for if a feral horse broke down a cat-proof, rabbit-proof or fox-proof fence, it could mean absolute disaster for that once protected environment.
They compete with native wildlife for food and habitat. With their weight they can cave in burrows of native marsupials, rodents and lizards. They compact the ground, see Soil Erosion and Land Degradation, and prevent re-habitation as the ground is too hard. They force kangaroos and other native grazing animals out of their habitat due to lack of food, and the feral horses’ ability to travel 50 kilometres for a source of water or their ‘home’ range for food.
The tracks and compacting made by hooves can also change the flow of water and run-off. Water flows downward and if a track made by a herd of feral horses creates an ‘alternate route’ for the water, the catchment area could dry out and if that catchment area supplies some type of agriculture, industry or housing estates with water, then this source wouldn’t be reliable and it would impact on the costs a lot to either remedy the situation or by having to change water sources.
They can carry exotic diseases such as African Horse Sickness and Equine Influenza which are harmful diseases and can effect domestic horses and cost the industry millions of dollars.