In this paper, we measure the degradation of the W Reserve in West Africa using the number of cases of illegal farming and illegal cattle grazing recorded and analyze the factors influencing such degradation using nonlinear Seemingly Unrelated Regression (SUR) model. Our results indicate that the Reserve degradation was negatively correlated with the average income level, the number of financial institutions, and the distance while a positive correlation with the average farm areas in the villages. The institutional characteristics of the villages, namely the number of non-governmental organizations promoting nature preservation, and the existence of check points between the Reserve and the villages in its periphery were negatively correlated with its degradation. Keywords: W Reserve, West Africa, illegal farming, illegal cattle grazing Acknowledgement : We thank Auburn University for providing funding support. We are also grateful to the administrations of the W Reserve in Benin, Burkina-Faso, and Niger for the provision of some of the data used in the study as well as to the municipalities in the periphery of the Reserve.