Review of the underpass alocation on the highway SP-225, Brotas-SP, Brazil, and the relationship with wild animals roadkills and landscape structure

Abstract

The Road Ecology theme is new in Brazil and in Latin America in \ud general. Few studies and scientific publications were made in this area \ud with specific and replicable methodology. Underpasses were allocated on \ud the highway SP- 225, in the year of 2008, according to previous studies of \ud hotspots of roadkills made by IBAMA (Environmental Brazilian Institute), \ud but none of them considered the influence of the landscape structure on \ud the surrounding habitat. So, we aimed to analyze and understand which \ud component of the landscape structure can influence the roadkills in a \ud Brazilian highway and analyze if these underpasses was located in areas \ud of hotspots roadkills. Medium and large mammals carcasses were \ud collected by Centrovias (a private enterprise that managed the road) from \ud May 2005 to June 2006 in 56 km stretch on the highway SP- 225 in the \ud 110 \ud city of Brotas, São Paulo, Brazil. Were created occurrences reports for \ud each roadkilled animal containing: date, time, local on the highway (km + \ud m), geographic coordinate and the specie affected. Forest-patch metrics \ud (number of fragments, proportion of forest and size of the largest pacth) \ud were extracted from a 2008 CBERS 2B-CCD image using Fragstats \ud (version 3.3) to examine the best predictor to medium and large \ud mammals roadkills. Following a visual classification three land cover \ud classes were mapped (forest, non-forest and water) and 13 buffers zones \ud with 5 km were selected around the highway SP-225. An exploratory data \ud analysis was conducted through the Pearson‟s correlation and 6 models (1 \ud null model) were built to conduct a model selection procedure based on \ud the AICc value. There were 48 medium and large mammals roadkills on \ud the 56 stretch sampled between May 2005 and June 2006. The best model \ud selected to predict medium and large mammals roadkills on the SP- 225, \ud was the proportion of forest (wAICc = 0.97) on the 5 km surrounding \ud habitat. From 13 buffer zones analyzed, 4 presented the highest number \ud of roadkills (mean = 21.75, sd = 2.21) and the highest proportion of \ud forest (mean = 24.17, sd = 2.34), so the higher the proportion of forest, \ud higher will be the number of roadkills. In two of these buffer zones were \ud allocated an appropriate number of underpasses. In all the buffer zones \ud we had roadkills occurrence, but in three of them none underpass was \ud allocated. Despite the fact that there is a low number of roadkills in these \ud buffers (range: 2-4) the presence of at least one underpass will be \ud necessary to avoid these roadkills. The others buffers also had a low \ud number of roadkills (range: 4-6) but there are almost the same number of \ud underpasses allocated in the buffers zones with the higher number of \ud roadkills. The number of roadkills is strictly related to the proportion of \ud forest in the surrounding habitat, so we highlight the importance of the \ud landscape structure to predict the occurrence of medium size and large \ud bodied mammals roadkills and the use of this tool to allocate underpasses \ud in future road ecology studies