Ecological Engineering 53 (2013) 31–38
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Ecological Engineering 53 (2013) 31–38 Contents lists available at SciVerse ScienceDirect Ecological Engineering j ournal homepage: www.elsevier.com/locate/ecoleng Evaluation of the effectiveness of a wildlife roadkill mitigation system in wetland habitat Alex Bager ∗, Vanessa Fontoura Road Ecology Research Group, Ecology Sector, Department of Biology, Federal University of Lavras, Campus Universitário CP 3037, Lavras, MG, CEP 37200 000, Brazil a r t i c l e i n f o a b s t r a c t Article history: This study assessed the effectiveness of a wildlife protection system (WPS) installed along a 15.7 km Received 7 March 2012 section of a federal highway in southern Brazil, which crosses through a federally protected area. The Received in revised form WPS has three sections and includes 19 underpasses, fences along two sections, and stock guards at the 22 December 2012 beginning and end of each section. Monitoring was carried out from 1995 to 2002. The changes in the Accepted 16 January 2013 roadkill rate (number of individuals/km/day) and the community of vertebrates affected by the WPS were analyzed. A total of 32 taxonomic units (TUs) were identified. Mammalia was the class with the highest Keywords: richness of TUs affected before (S = 12) and after (S = 13) the installation of the WPS. For both pre- and Wildlife mortality Fence post-WPS stages combined, mammals had the most roadkilled individuals (92.2%), followed by reptiles (5.2%). The highest roadkill rates were observed in winter 1995 (0.38 0.291 ind./km/day), winter 1998 Mitigation ± Roadkill (0.20 0.130 ind./km/day), and autumn 2002 (0.17 0.123 ind./km/day). Overall, the WPS reduced the ± ± Vertebrates mortality of the main species affected, Myocastor coypus; however, except for this species, the roadkill Wetlands rates remained steady. Several modifications in the initial design are suggested to improve the system. © 2013 Elsevier B.V. All rights reserved. 1. Introduction results from roadkills, but they must also permit the maintenance of ecological processes such as movement, genetic change, and con- Roads are vectors of socio-economic development and are vital nectivity. To ensure efficiency, these measures must consider the for the growth of a country. However, roads also have nega- specific requirements of the focal species (Forman et al., 2003). Mit- tive impacts such as habitat degradation, dissemination of exotic igation systems can be implemented to protect one species (Cain species, and loss of biodiversity through roadkill and landscape et al., 2003), a few species (Aresco, 2005) or the entire community fragmentation (Trombulak and Frissell, 2000). When these effects affected by roadkills (Dodd et al., 2004). It is obviously most dif- occur within or around protected areas, the problem becomes more ficult to protect an entire community, which requires knowledge serious because such areas usually have higher concentrations of about the species involved, including body size, habitat, movement species and large numbers of individuals (Bager, 2003). Forman capacity and geographic distribution. et al. (2003) stated that rather than worrying about the impacts of Studies on the use of passages and fences have increased, though roads on a particular species, it is more important to consider one only a few works have analyzed the effectiveness of a mitiga- of the greatest contemporary problems for conservation, which is tion system after its implementation (Mata et al., 2005). When the loss of ecological processes at the population, community and effectiveness analysis is realized a new problem that arises is ecosystem levels. Roads, as well as other linear projects, can acutely the inappropriate experimental design, without prior information affect all of these levels, generating both short-term, high-intensity and control areas, making the data insufficient and inconclusive impacts as well as chronic impacts of varying intensities. (Lesbarrères and Fahrig, 2012) and discuss the importance of Strategies taken to mitigate the impacts of roads may include Before-After-Control-Impacts (BACI) design studies. BACI design the installation of speed reducers, active or passive signals, fences, has been widely used to assess impact on streams (Roley et al., air passages, and underpasses (Dodd et al., 2004; Glista et al., 2012), wind farm (de Lucas et al., 2005), power lines (Barrientos 2009; Grilo et al., 2010; Romin and Bissonette, 1996). These strate- et al., 2012), but despite the potential there are few examples gies are aimed toward the reduction of wild-animal mortality that for roads (Goosem et al., 2001; Lesbarrères and Fahrig, 2012). Our study has all elements of a BACI design (see Roedenbeck et al., 2007) and had the objective of assess the effective- ness of a mitigation system installed in a Brazilian protected ∗ Corresponding author. Tel.: +55 35 3829 1928. E-mail addresses: [email protected]fla.br, [email protected] (A. Bager). area. 0925-8574/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ecoleng.2013.01.006 32 A. Bager, V. Fontoura / Ecological Engineering 53 (2013) 31–38 Fig. 1. Schematic representation of the section of highway BR 471 where the wildlife protection system (WPS) was implemented in the Taim Ecological Station. The road was divided into three sectors, with underpasses along its length (c), four stock guards (b), and fences in sectors 1 and 3 (a). The road is bordered by wetlands and ponds (Cut D – D′). This system was proposed to minimize roadkills of Myocas- 471. The WPS comprises three sectors. Sector 1, in the northern tor coypus and Hydrochoerus hydrochaeris, although this is not part of the system, is 3.4 km long, with a continuous fence along documented. For many years, there was public pressure on the both sides of the road. The middle sector, sector 2, is 5.5 km long administrators of the protected area, due to the omnipresence of and unfenced. Sector 3, to the south, is again fenced along its entire large mammal carcasses along road edges and because occasional 6.8 km length. Sectors 1 and 3 are located where BR 471 is tangent serious accidents resulted in human mortality and extensive prop- to the edge of the Taim ESEC, and in sector 2, the road cuts through erty damage. Although the primary focus is on these two species, the protected area. The fences were installed on a concrete base there was always the expectation that this system can be effective that is 0.2 m above the ground and is buried to a depth of 0.4 m. for multi-species, including of small size and birds. Thus, we define The lower portion of each fence, which is 0.65 m high, is composed a complementary aim to analyze the changes in roadkill rates and of square, 50 mm mesh, while the upper portion of the fence con- the faunal community before and after the implementation of the sists of 100 mm mesh that is 0.45 m in height. At the beginning and system. end of each sector, a stock guard was installed to prevent animals from entering the fenced sector and to reduce the probability that they will move along the road. These stock guards are 11.2 m wide 2. Materials and methods and 2.4 m long. The WPS also has 19 round underpasses that are 1.6 m in diameter; there are four underpasses in sector 1, nine in 2.1. Study area sector 2, and six in sector 3. The arrangement of these underpasses was established by the engineering company that constructed the The Taim Ecological Station (Taim ESEC) (32◦ 32′ 14.44′′S; 52◦ WPS (Fig. 1). 32′ 18.67′′W) is a federal protection area located on the coastal plain of the state of Rio Grande do Sul, Brazil. The ecological station has an area of 33,818 ha; the relief is low and flat and wetlands are 2.2. Roadkill survey predominant, though open fields and dunes are present too. The cli- mate is mild, with a cold, rainy winter and a warm, dry summer. The Technicians from the Taim ESEC carried out daily road moni- mean annual precipitation is 1100 mm, and the mean temperature toring from July 1995 through June 2002. Over this 84-month time is 18 ◦C (Nimer, 1989). period, no monitoring occurred in 11 months (January, November This highway is more than 600 km long, with a 15.7 km stretch and December 1996; January 1997; February 1998; and June, July, passing through the park. In this section, the highway has two lanes August, September, November and December 1999). and is approximately 25 m wide, considering the shoulders. It was Samples taken from July 1995 through September 1998 were constructed by excavating soil along the route and forming a bor- considered to be part of the period before the installation of the row ditch along each side; the pavement is approximately 5.4 m wildlife protection system (pre-WPS), whereas samples taken from above water level. In addition to the borrow ditches, the surround- October 1998 through June 2002 were in the post-installation ing area contains extensive wetlands and flooded grassland. During phase (post-WPS). Sampling was performed from a car, at an aver- the autumn-winter rainy season, these fields may remain under- age speed of 50 km/h, by two to four observers, along the 15.7 km water for several months. In 1998, a wildlife protection system stretch where highway BR 471 passes through the Taim ESEC. A (WPS) was installed in Taim ESEC along the federal highway BR total of 619 monitoring runs were made during the pre-WPS, and A.