The methods are described in a series of manuscripts:

Ridding, L.E., Newton, A.C., Keith, S.A., Walls, R.M., Diaz, A., Pywell, R.F. and Bullock, J.M. (2020). Inconsistent detection of extinction debts using different methods. Ecography. doi:10.1111/ecog.05344
Ridding, L.E., Newton, A.C., Redhead, J. W., Watson, S.C.L., Rowland, C.S., and Bullock, J.M. (2020). Modelling historical landscape changes. Landscape Ecology, https://doi.org/10.1007/s10980-020-01059-9
Ridding, L.E., Watson, S.C.L., Newton, A.C., Rowland, C.S., and Bullock, J.M. (2020). Ongoing, but slowing, habitat loss in a rural landscape over 85 years. Landscape Ecology 35, 257–273.