prosecution is strongly needed (Nellemann et al., 2011). This also includes better regulation of fencing and managing the expand- ing livestock and cropland with specific reference to protecting wildlife migrations and seasonal habitat to avoid further declines in wildlife populations (Ogutu et al., 2011).
The effect of roads, expanding agriculture and livestock, along with increased poaching can also be observed in South America, such as on the wild camelids in the steppe, deserts and Andean foothills of Argentina and Chile. Guanacos (Lama guanicoe) and vicunãs (Vicugna vicugna) have lost 40–75 per cent of their rang- es, and probably dropped at least 90 per cent in their numbers over the last centuries (Cajal, 1991; Franklin et al., 1997). Only a fraction, probably less than 3 per cent of the guanaco and some 34 per cent of that of vicunãs are in protected areas (Donadio and Buskirk, 2006). Also these species often avoid areas with expanding livestock and have been heavily exposed to poaching.
While roads or railways rarely result in complete physical block- age, there is ample evidence and documentation that such in-
frastructure slows, delays or reduces the frequency of crossings substantially, increases risk of predation or poaching, causes expansion in agriculture along road corridors and subsequently habitat loss resulting in declines in migratory populations over time (UNEP, 2001; Bolger et al., 2008; Vistnes and Nellemann, 2009), thus impacting entire ecological networks involving a range of species.
Also here, international collaboration on enforcement as well as removal of barriers is critical. Indeed, migrations and habi- tat can sometimes even be restored if barriers to migrations, such as fences or infrastructure, are removed (Bartlam-Brooks, 2011). This even accounts for removal of trails or roads or hous- ing (Nellemann et al., 2010). In a study in Northern Botswana, a fence constructed in 1968 persisted up to 2004, and effec- tively hindered migration of the plains zebra (Equus burchelli antiquorum) between the Okavango Delta and Makgadikgadi grasslands (a round-trip distance of 588 km), revealed that only after four years some zebra had already reinstated this migra- tion (Bartlam-Brooks, 2011).