maes

This function uses the method presented in Maes et al, (2012) to estimate a percentage change in distribution area between two time periods. The formula attempts to account for uneven recording effort between time periods. This method is specifically designed to feed into IUCN red list analyses (criterion A2c). This function can take multiple time periods and will complete all pairwise comparisons.

This method only includes sites that fulfill a criteria set by min_sp. This parameter gives the minimum number of species that must be observed in both time periods for a site to be included. For example, if set to 5, then at least 5 species much be observed in both time period 1 and time period 2 for that site to be included in the analysis.

# Load the library
library(sparta)

# Load example dataset
data(ex_dat)

# Run the analysis
Ma_out<-maes(Data=ex_dat,
             time_periods=(data.frame(start=c(1980,1990,2000),end=c(1989,1999,2009))),
             min_sp=1,
             site_col='hectad',
             sp_col='CONCEPT',
             start_col='TO_STARTDATE',
             end_col='Date')

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###References

Maes, D., Vanreusel, W., Jacobs, I., Berwaerts, K., Van Dyck, H. (2012) Applying IUCN Red List criteria at a small regional level: A test case with butterflies in Flanders (north Belgium). Biological conservation, 145, 258-266.