Feral livestock as a potential threat to treelike cacti-dominated arid landscapes: a case from the Argentinian Monte Arido

ACEBES, P.; TRABA, J.; OVEJERO, R.; BORGHI, C.; CAMPOS, C.; PECO, B. & MALO, J.E.

Congreso; 20th Annual meeting of the Society of Conservation Biology (SBC); 2006

Species introduction and naturalization represent a serious threat for many natural protected areas and one such case of worldwide concern is feral livestock in arid ecosystems. Damage suffered by the treelike cacti (<i>Trichocereus terscheckii<i/>) dominating the landscape of rocky slopes was surveyed in 7 locations within the Ischigualasto<en>Talampaya World Heritage Site (Argentina) by measuring the number, position and size of damages. In parallel we estimated the abundance of large herbivores (<i>Lama guanicoe<i/>, <i>Bos taurus<i/>, <i>Equus assinus<i/>) through dung transects. Results show relatively high damage levels (40<en>77<percent> damaged individuals) and their concentration within the 0.50<en>1.75 m high range (chi<en>squared test, p<0.001) strongly suggesting herbivores to be the main responsible of them. Moreover, we find significative differences among sites in variables measuring damage level  (ANOVA test, p<0.001) and in the intensity of use by herbivores, both for guanaco (Kruskal<en>Wallis test, p<0.05) and for the two feral livestock species (p<0.001). Finally, damage levels are correlated with frequencies of cattle and donkey dung in transects (Spearman r, p<0.05), but not with that of guanaco. We conclude that the continued presence of feral livestock gives rise to damages to treelike cacti potentially affecting their populations and threatening the physiognomy of the protected landscape.