Results of CCA analysis: biplot of the environmental variables and the densities of native and non native species. Eigenvalues of axis 1 and 2 were 0.150 and 0.027, respectively. The first two axes explained 77.20% of total variance. The length of the arrow is proportional to the rate of change; a long arrow indicates a large change and that the change is strongly correlated with the ordination axes.