Hur utvärderas faunapassager? - En litteraturstudie om säkra passager för djur över vägar och hur de utvärderas
Sammanfattning: Habitat fragmentation is a common problem in relation with road infrastructure which leads to mortality, isolation of animal populations, and has a negative effect on biodiversity. Animal crossings have been implemented in many countries and are a useful tool to mitigate these problems but they are expensive to build. This thesis explores the methodological approaches used to evaluate how wildlife crossings’ functions are evaluated. This was done by reviewing abstracts from a total of 223 peer-reviewed scientific publications. There were a great variety of methods used to evaluate crossing, but cameras was the most commonly used. Many studies used a combination of methods to make up for shortcomings with the single methods, for example, using PIT to make up for cameras inability to identify individuals crossing the passage. The results show that it is important to evaluate the passages and associated structures, like fences, for many factors and not focus on only one. Cameras are a good option for monitoring the use of a passage, but it is key to understand that animals using the passage does not equal a positive effect on their populations. It is therefore important to evaluate how populations are affected and whether they are viable or not. This was done by using Population Viability Analysis, evaluating populations’ genetic variation, or evaluate whether the passage allows for gene flow to occur. DNA-analysis is sometimes required for this and can now be done with a more inexpensive and simple method, using hairs from animals, collected in a non-invasive way. It is also important to evaluate the passage both before and after to be able to determine the actual effect the passage has had. But nothing ever stays the same, and the passage should be monitored for longer periods or at regular intervals to make sure a satisfactory effect is sustained.
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