The role of massive infrastructure projects on the spread of invasive non-native species and its effects on semi-arid regeneration

Abstract

Massive infrastructure projects (MIP) are becoming more common around the world to meet the needs of a growing human population. There is evidence of such structures facilitating biological invasions. The implementation of MIP involves numerous forms and mechanisms of land-use transformation, such as opening of access roads, deforestation, and intense movement of land, people and machinery that degrades the habitat and creates opportunities for colonization of new species. This degradation could lead to the establishment of invasive non-native species, considering they often have the ability to colonize disturbed sites, and to negatively affect natural regeneration. In this study, we used one of the largest MIP under development in Brazil (Projeto de Integração do rio São Francisco - PISF) to assess the relationship between land-use transformation imposed by MIP and the establishment and spread of non-native species. We determined if PISF acted as a dispersal route for non-native species and which non-native species may be benefiting from PISF to proliferate. Further, we verified the effects of the main invaders on the plant regeneration of the study area, and tested if the plant richness of the invaded sites differed among invaders. Our results confirmed PISF as a route for the dispersal of non-native species. Monitoring surveys recorded 21 non-native plant species in PISF’s deployment area (DA). Species were established in several artificial and natural habitats, and widespread across most of the study area. Eleven years after the DA was completely deforested, 92.3% of its extension had non-native plant populations. Calotropis procera, Nicotiana glauca, and Prosopis juliflora were the most relevant non-native species in PISF. The relationship between land-use transformations and the widespread distribution of invasive species demonstrate that MIP can act as corridors for the spread of these species. We found that invaded sites presented significantly lower plant richness than non-invaded sites and there were differences in richness among invasive species. The invasion of non-native species was the main factor for the difference between invaded and non-invaded communities. The identity of the invasive species explained only a small part of this difference. Also, C. procera showed significant differences in relation to both of other invaders. In contrast, N. glauca and P. juliflora did not differ each other. The highest mean and absolute richness in sites dominated by C. procera indicates greater tolerance to co-occurrence of native species.