Is spillover all it seems? Investigating how reserves affect their surrounds.Posted: May 4, 2014
by Rebecca Davies
Many of us expect the benefits of reserves to spread beyond their boundaries, but is this really the case? And if not, how can spillover from reserves be improved? Reserves, such as national parks and no take zones, are a common way to practice conservation which ensures the protection of wildlife within their boundaries. They are important for protecting rare and important areas, such as breeding grounds or endangered populations. Well planned and managed reserves benefit surrounding areas through export of biodiversity and resources, a phenomenon known as ‘spillover’, but sometimes reserves can have negative effects on their surrounds. Wildlife from reserves threatens livelihoods and an influx of tourists degrades resources. Where wildlife is perceived to be a threat there are poaching, retaliation and compensatory killings. To reduce these negative impacts it is important to carefully consider reserve design, ensure farmers are protected and compensated when wildlife causes harm, limit hunting, and create education programmes. The positive results of reserves can spill over, but only if reserves are effectively designed and managed.
Supporters of marine reserves often use the argument that reserves provide spillover of commercially important species, but is this the case? In some cases it is, such as Apo marine reserve in the Philippines. The creation of Apo reserve has resulted in greater species richness and predatory fish abundance both within and outside of the reserve leading to a community more similar to a natural un-fished one (Russ & Alcala, 2011). Marine reserves also exhibit recruitment spillover, for example reserves in Norway protect large fecund lobsters, increasing recruitment and leading to larval drift from the reserves to habitat over 20km away (Huserbraten et al., 2013). Similarly, Clown fish larvae from a reserve in Papua New Guinea have been shown to drift up to 35km away (Planes, Jones & Thorrold, 2009). Through these increases in species richness, trophic structure, and recruitment the benefits of marine reserves can spill over.
There are fewer examples of positive spillover from terrestrial reserves, possibly because terrestrial environments tend to be less connected and reserves are often islands in a sea of unsuitable habitat. There is nowhere for wildlife to go outside of many terrestrial reserves, as shown by Image 1, in contrast to marine reserves where the wildlife can migrate freely. However, ecosystem services can pass out of reserves and benefit surrounding areas. For example, Gaoligongshan reserve in southwestern China provides services such as water to the local environment (Allendorf & Yang, 2013). Local villagers especially appreciate the reserve when these services are most needed, such as during droughts (Allendorf & Yang, 2013). Resource spillover from reserves is valuable, but the disconnected nature of terrestrial reserves mean wildlife spillover is limited, this may be remedied by increasing connectivity to suitable habitat so wildlife can migrate more freely.
Wildlife spillover is also limited by hunters acting as a barrier to migrating wildlife, compounding any lack of landscape connectivity. In marine environments this is known as ‘fishing the line’, and concentrates harvest efforts into a small area along the reserve boundary (Kellner et al. 2007). This greatly reduces the densities of some species, driving spatial patterns and reducing spillover (Kellner et al. 2007). Removing fish migrating out of reserves leads to a depression in fish numbers directly beyond the boundaries and creates an edge effect (Kellner et al. 2007). Edge effects are modifications of the environment near to an edge, in this case mortality increases and benthic habitat is destroyed by destructive fishing practices (Kellner et al. 2007), as shown in Image 2. Fishing reserve boundaries can effectively stop biodiversity spillover from reserves and needs to be considered in reserve network designs to maintain migration corridors (Kellner et al. 2007).
In terrestrial environments, hunting along boundaries has a similar effect. This is illustrated in India, where wildlife leaving reserves are killed as retaliation for harming people or raiding crops, effectively stopping emigration (Karanth et al., 2013). Similarly, people around the Serengeti National Park kill any wildlife perceived as a threat (Holmern, Nyahongo & Roskaft, 2007). In Peru large carnivores such as pumas are routinely removed from near human settlements and farmers compensate for crop and livestock losses by hunting bushmeat, leading to large wildlife being killed disproportionately (Naughton-Treves et al. 2003), potentially leading to a change in the trophic structure of the ecosystem. To increase biodiversity spillover retaliation and compensation killings need to be reduced by protecting crops and livestock.
Communities surrounding reserves are also negatively affected by irresponsible tourism practices which have disastrous consequences for the environment. Stara Reka reserve in Bulgaria contains many rare plants and sees high tourism levels (Yocheva et al. 2013). Visiting tourists dispose of waste in nearby areas, creating pollution and attracting bears out of the reserve where there are increased rates of poaching (Yocheva et al. 2013). Tourists have also caused several wildfires that have spread through the reserve into surrounding areas (Yocheva et al. 2013). In Central Karakoram National Park, Pakistan, tourists negatively affect services that locals rely on, for example porters cut wood for fires and walking sticks, and there is a massive accumulation of human waste and rubbish both within and outside of the reserve (Imran, Alam & Beaumont, 2014). To reduce negative effects and increase spillover of ecosystem services irresponsible tourism needs to be addressed.
Thankfully, there are solutions to the problems identified above. Problems caused by tourism can be solved, or at least reduced, by increasing the facilities available within reserves and providing education (Imran, Alam & Beaumont, 2014; Yocheva et al. 2013). Tourists and tourism operators often have inadequate knowledge about the environment and sustainable tourism practices, so education is important to increase environmental awareness and sustainable behaviours (Beaumont, 2014). Retaliation and compensation killings can be reduced by offering compensation for losses so that farmers do not need to kill wildlife to survive (Karanth et al., 2013). Livestock and crops can be protected from wildlife by avoiding grazing within reserves, which increases livestock killings, and by reducing crop diversity, which means crops are not available for as long so reduces raiding (Karanth et al., 2013). Fencing and guard animals, shown in Image 3., protect crops and livestock (Karanth et al. 2013). Once farms are protected, limiting hunting is key to increasing spillover, as hunting levels, rather than habitat changes, determine wildlife survival beyond reserve boundaries (Naughton-Treves et al. 2003), and, as previously mentioned, hunters act as a barrier to migrating wildlife. Hunting and fishing practices need to be included in reserve network designs to increase connectivity (Kellner et al. 2007). Programs such as MARXAN incorporate economic and environmental spatial data to design reserve networks to increase connectivity and therefore spillover (White et al., 2013). Planning how the land outside of reserves is utilised further enhances spillover by connecting areas of high environmental value and allowing for development of areas with high commercial value (Karaksela et al., 2013). Educating tourism operators, protecting farms, limiting hunting and carefully planning reserves will increase connectivity and spillover.
Engaging stakeholders in reserve planning is essential as people with a high connection to an area value the quality of the environment more, while exclusion from planning reduces support of reserves and conservation (Beaumont, 2014). There are also economic links to environmental attitudes, for example those that benefit from trophy hunting are more likely to want to protect the environment than those who see no economic benefits (Beaumont, 2014). This is illustrated by the Sariska Tiger Reserve in India which provides locals with income through tourism, accounting for their positive attitude towards the reserve and conservation in general (Sekhar, 2003). In this way the benefits of reserves spillover by altering attitudes so people care more about protecting the environment. Engaging stakeholders in the planning and economic benefits of reserves improves attitudes and behaviours.
From the above examples, it is clear spillover is occurring, ranging from biodiversity and recruitment exports from marine reserves to ecosystem services from terrestrial reserves, but this is not always the case. Spillover is prevented by hunting and reserves have negative effects on their surrounds through livestock and crop losses and irresponsible tourism. So how can spillover be improved? Through an increase in connectivity and decrease in the negative effects of tourism. For this to happen, reserves need to be planned in a way which maximises connectivity, and there needs to be farm protection, hunting regulations, and tourism education programmes put in place. By careful planning of reserve networks, fishing the line can become less important due to larval drift and maintenance of migration corridors, and terrestrial reserves can make use of areas of low commercial value to increase connectivity. This connectivity is maintained by reducing wildlife killings through compensation and farm protection. Hunting regulations allow larger animals and more carnivores to migrate out of reserves and spillover into surrounding areas. Educating tourism operators will reduce pollution and resource degradation, while involving locals in the benefits and planning of reserves increases support. Spillover is not necessarily occurring around most reserves, but with a few changes it could be.
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