Sampling alien species inside and outside protected areas: does it matter?

TL;DR

This study investigates whether data on alien species in protected areas can be generalized to non-protected regions, finding that protected areas may underestimate alien species richness due to lower human disturbance.

Contribution

It provides an analysis of alien species distribution in protected versus non-protected areas, highlighting the importance of human activity factors in such assessments.

Findings

Protected area percentage is a poor predictor of alien species richness.

Cells with more protected areas tend to have slightly fewer alien species.

Human activities influence alien species distribution more than protection status.

Abstract

Data of alien species presences are generally more readily available in protected than non-protected areas due to higher sampling efforts inside protected areas. Are the results and conclusions based on analyses of data collected in protected areas representative of wider non-protected regions? We address this question by analysing some recently published data of alien plants in Greece. Mixed effects models were used with alien species presences in 8.25 x 8.25 km cells as dependent variable and the percentage of protected area, as well as the agricultural and artificial land cover types richness (as indicators of human presence) as independent variables. In addition, the spatial cross-correlation between the percentage of protected area and alien species richness was examined across scales. Results indicated that the percentage of protected area per cell is a poor predictor of alien species richness. Spatial analysis indicated that cells with higher percentage of protected areas have slightly less alien species than cells with lower percentage of protected areas. This result is likely to be driven by the overall negative correlation between habitat protection and anthropogenic activities. Thus, the conclusions deduced by data deriving from protected areas are likely to hold true for patterns of alien species in non-protected areas when the human pressures are accounted for.