Figure 6

Frequency distribution of summed human population counts in 6 randomly selected grid cells in sub-Saharan Africa. The distribution was constructed from 10,000 sampling runs and compared to the observed summed human population counts in the 6 grid cells where invasions were observed (red line). Grey zone indicates the 95% samples with lowest human population counts. Only 2 of the 10,000 random sampling runs resulted in sums higher than the observed value, suggesting that invasions were non-random with respect to human population (as a proxy for anthropogenically-induced stress).