The manual deals with the extension of agricultural surfaces and ecological risks in the province of Moyen-Ogooué, the case of Siat Gabon in Lambaréné. The goal here is to understand the different practices of agribusiness on the one hand and the preservation of the environment on the other. Should we continue to use chemical products for agriculture? How to develop a reasonable agriculture? What are the different impacts and risks caused by the use of agricultural pesticides? These are some of the questions that we try to answer in this manual.