Canals as invasion pathways in tropical dry forest and the need for monitoring and management.
Linear infrastructure intrusions are common around the world to meet the needs of a growing and interconnected human population. The implementation of linear infrastructures involves numerous forms and mechanisms of land-use transformation that can facilitate and serve as pathways to the spread of invasive non-native species. However, the type and intensity of land transformations change over time and this can affect the frequency and intensity in which linear infrastructures route the spread of invasive species. Here, we present results collected over 5 years of monitoring surveys (2015-2019) to assess the relationship between the construction of one of the largest canals to date in Brazil and the spread of non-native species. We studied the Integration Project of the São Francisco River (PISF), a canal fully inserted in the Caatinga biome, a tropical dry forest ecosystem for which information on invasion dynamics are little known. Our results confirmed PISF canals served as habitat and dispersal corridors for non-native plant species. Monitoring surveys recorded 26 non-native species established along the 83.2 km2 PISF deployment area. Eleven years after the canal deployment area was completely cleared of vegetation, 92.3% of its extension had non-native plant populations. Of the 10 species assessed for their population status, 8 had invasive populations. The time immediately after construction work finished was the critical stage for the spread of non-native woody plants, which increased their distributions with reduced levels of construction intervention, whereas most of the herbaceous species reduced their distributions. When human intervention was drastically reduced, many populations of non-native plants rapidly formed at the deployment area. Policy implications. Man-made linear infrastructures can remove biogeographical barriers and serve as pathways for the spread of invasive species over long distances and across ecosystems. Thus, the planning, construction and management of such infrastructures should include measures and funding for risk assessment, prevention, monitoring and control of biological invasions. Agencies responsible for environmental licensing should mandate invasive species management as part of the installation and operation licensing conditions.