The Pervasive Impact of Humans
Despite the existence of many large protected areas where human impacts are minimised, just about all predator-prey systems on earth are impacted by humans in various ways. The most obvious and immediate effect is through human induced mortality of both predators and prey. While some of the planet's largest protected areas may insulate some large herbivores from human exploitation, there is still pervasive human impact through poaching and legal harvest within protected areas or on the herbivores that seasonally migrate outside the borders. For large carnivores, the situation is even worse as their wide-ranging movements more often carry them beyond protected area borders (Woodroffe and Ginsberg 1998). In a European context, where protected areas are often small, there are probably very few large predator individuals, let alone populations, that live their lives entirely inside protected areas (Linnell et al. 2001).
In addition to the deliberate targeting of these species, there are many other sources of mortality which humans induce, such as through vehicle collisions (Langbein et al. 2011) and cases where disease is transferred from domestic to wild species. Furthermore, humans have very strong impacts on herbivores through their manipulation of habitats (see Chap. 8). Forestry and agricultural practices have dramatic impacts on vegetation structure and productivity that can have both positive and negative impacts on herbivore and carnivore populations (e.g. Gill et al. 1996; Torres et al. 2011). In general, small scale forestry and agriculture lead to situations that increase productivity and benefit many herbivores. The winter feeding of wild herbivores is a widespread activity across most of northern, eastern and central Europe which has the potential to greatly influence herbivore distribution and density (Putman et al. 2011). Long-term deposition of nitrogen and climate change can also have dramatic impacts on the productivity of vegetation (Holland et al. 2005). Another impact comes from competition between domestic and wild species. Domestic herbivore densities tend to exceed those of wild herbivores and can have dramatic impacts on habitat structure and the productivity of vegetation, as well as providing potential prey items for predators. In many areas, animals of domestic origin have been, and still are, critical prey for large carnivores (Mattisson et al. 2011; Peterson and Ciucci 2003). Even predators of domestic origin (domestic cats and dogs) can compete with wild predators. A final impact occurs through the behavioural disturbance that human presence and activity can induce in both predators and prey (Moen et al. 2012). Given the mobility of both large carnivores and large
herbivores, the spatial impacts of these diverse perturbations are likely to influence the structure and functions of populations on scales of at least tens and hundreds of kilometres. Across Europe, there is a very high degree of diversity in the ways habitats, herbivores and carnivores are managed, such that actions in neighbouring countries could well have dramatic impacts on predator-prey dynamics even beyond their own borders (Putman et al. 2011; Kaczensky et al. 2013; Linnell and Boitani 2012).
Despite the pervasive impacts of humans, the recent history of large carnivore and large herbivore recovery in Europe has shown that these species have a remarkable ability to persist and thrive in human-modified landscapes. There are clear species-specific differences in this tolerance, with wolves and roe deer for example being especially tolerant of modified landscapes, and species such as bears and wild reindeer being least tolerant. Certainly there are limits to tolerance. Extreme habitat modification for intensive agriculture and high rates of disturbance can make many areas unliveable for many species (e.g. Schadt et al. 2002; Güthlin et al. 2011; Jedrzejewski et al. 2008). A lot of transport infrastructure has the potential to create barriers (Kaczensky et al. 2003). However, in general none of these species require areas free of human intervention, and most will in fact benefit to some extent from many low-intensity human activities (Basille et al 2009; Torres et al. 2011).