The objective of this study is to identify changes in the vegetation cover in estimating crop fraction cover in the Brittany region over the 2000-2006 period. Biophysical products derived from current coarse and medium resolution sensors allow the detection of changes over landscapes made of large patches. In fragmented landscapes, the 1 km spatial resolution is not suited to identify changes in vegetation cover due to mixing effects. Higher spatial resolution is thus required to detect vegetation changes. We present an original method to estimate biophysical variables and particularly fCOVER at 250 m spatial resolution from EOS/MODIS-AM1 (Terra) sensor in using the combined PROSPECT-SAIL model The results obtained from this study highlight that MODIS fCOVER data at 250 m spatial resolution estimated with the PROSPECT+ SAIL model is related to field observations of green vegetation cover fraction.