I have modelled organism dynamics and abiotic factors time series in order to understand their seasonal oscillation and trend over time. Now I want to identify if there are any correlation between environmental variations and a lagged biotic response, using the cross-correlation function (ccf::stats).
Most of my biotic time series are not stationary, and even the detrended time series or residual series aren't either. I've realized differencing (using diff::stats) the time series changes drastically the structure, so I don't think it is very reasonable to use this approach. Since stationarity is fundamental for cross-correlation analysis, what alternative should I try?