Feral cattle can severely modify native vegetation by browsing, crushing and trampling (Aston 1912; Wodzicki 1950). In native forests they invariably lay bare the forest floor and eliminate nearly all young trees, shrubs and ferns, until only a few unpalatable or browse-resistant species remain. In subalpine environments feral cattle open up clearings by breaking down and browsing low-canopied vegetation. On sub-antarctic Enderby Island feral cattle prevented the regeneration of Poa litorosa tussock grassland and a variety of endemic sub-antarctic herbs (Parkes, 2005). Scott et al. (in Stone 1984) regarded domestic and feral cattle as the “single most destructive agent to Hawai‘ian ecosystems, particularly to koa forests”. Regeneration of young koa (see Acacia koaia in IUCN Red List of Threatened Species) trees is completely suppressed in some forests of Hawai‘I (Baldwin and Fagerlund 1943; SPREP, 2000).
Degradation of breeding sites by introduced cattle has decreased the range and population of the 'critically endangered' Amsterdam albatross (see Diomedea amsterdamensis in IUCN Red List of Threatened Species). Across the island (BirdLife International 2007).
Location Specific Impacts:
Anegada Is. (British Virgin Islands)
Habitat alteration: Vegetation changes caused by grazing cattle will also be affecting birds lizards and bats (Veitch, 1998 in Varnham, 2006).
Threat to endangered species: Cattle, Bos taurus, are believed to be the major factor in changing food availablility to the 'Critically Endangered (CR)' Anegada Is. rock iguana (see Cyclura pinguis in IUCN Red List of Threatened Species) on Anegada Is. (Veitch, 1998 in Varnham, 2006).
Falkland Islands (Malvinas) (sub-Antarctic)
Disease transmission: There is a risk that cattle may transmit bovine TB.
Habitat alteration: Cattle have been implicated in loss of tussac grass (Parodiochloa flabellata), fachine (Chiliotrichum diffusum) and changes in vegetation composition (McDowall et al., 2001 in Varnham, 2006).
Reduction in native biodiversity: Cattle may play a possible role in extinction of some plant species (McDowall et al., 2001 in Varnham, 2006).
Rapa Is. (French Polynesia)
Habitat alteration: Very few details are available on the impact of wild populations of cattle but it seems to be significant. The landscape has been significantly modified and vegetation cover has been greatly reduced (Meyer, pers. comm., 2007).
Interaction with other invasive species: Cattle spread the seeds of Psidium cattleianum (Meyer, pers. comm., 2007).
Amsterdam Is. (sub-Antarctic) (French Southern Territories)
Threat to endangered species: Before 1988, when a portion of the herd was slaughtered and a fence constructed, cattle wandered over on the whole island. Colonies of the endemic Amsterdam albatross (see Diomedea amsterdamensis in IUCN Red List of Threatened Species) were threatened through destruction of their nesting habitats by the trampling and grazing of wandering cattle (Micol and Jouventin, 1995). Native vegetation such as Phylica nitida, the only endemic tree in French Southern and Antarctic Territories, was also under pressure from significant grazing. Plant communities were largely dominated by resiliant introduced species that respond well to grazing.
Grand Terre Is. (New Caledonia) (New Caledonia (Nouvelle Caledonie))
Habitat alteration: Wild cattle contribute to the degradation of remnants of dry forests (De Garine-Wichatitsky et al., 2004).
Interaction with other invasive species: Cattle are probably involved in the spread of invasive plants especially grasses (De Garine-Wichatitsky et al., 2004).
Reunion (La Reunion)
Habitat alteration: In forests of the endemic tree Acacia heterophylla, livestock considerably limit natural regeneration and convert grass and shrub layers into large pastures (Triolo, 2005).
Interaction with other invasive species: Cattle are involved in the spread of invasive alien plants especially grasses.
Turks and Caicos Islands
Threat to endangered species: Bos taurus may compete for grazing with or trample burrows of native rock iguanas (Mitchell et al., 2002 in Varnham, 2006).
B. taurus pose a serious threat to the 'Critically Endangered (CR)' Turks & Caicos rock iguana (see Cyclura carinata in IUCN Red List of Threatened Species) , presumably through competition for food plants, altering the vegetational composition of habitats and trampling soft substrates where iguanas burrow or nest (Alberts, 2000 in Varnham, 2006).
Hawaii (Hawai‘i) Is. (United States (USA))
Reduction in native biodiversity: Domestic and feral cattle are regarded as the “single most destructive agent to Hawaiian ecosystems, particularly to koa forests”. Regeneration of young koa (see Acacia koaia in IUCN Red List of Threatened Species) trees is completely suppressed in some forests of Hawaii. Cattle grazing was considered to be a primary factor in the decline of an endemic leguminous vine (see Vicia menziesii in Protection) on the island of Hawaii. Cattle browsing was more destructive to mammane (Sophora chrysophylla) forests on Mauna Loa volcano, than sheep browsing.