add CHELSA climate

[AMBarbosa]

It would be great if you could add also CHELSA (https://chelsa-climate.org/) for terrestrial climate. Comparison papers have found it superior to WorldClim, probably because it is based on statistical downscaling rather than spatial interpolation of very irregularly distributed weather stations. Cheers!

[salvafern]

Hi @AMBarbosa. Thank you for opening the issue, I was not aware of the existence of this dataset and indeed seems a valuable addition for sdmpredictors.

Unfortunately I don't have time to get to know the CHELSA dataset. I was wondering if you could help? If you come up with a list of the layers to be included in sdmpredictors following the structure of layers.csv and layers_future.csv (most important: the url to the layer. This link is an example) I can then update sdmpredictors.

sdmpredictors currently supports layers as .tif, or anything that can be easily read with raster::raster(). Multidimensional formats like NetCDF are not supported yet.

Do you think you have time to do this?

[AMBarbosa]

I'm very short on time myself, but I'll try when I get the chance.