ReU has operated as a nature reserve for the conservation of Chihuahuan desert grasslands for the past 15 years; it encompasses 18,546 hectares in the heart of the Janos Biosphere Reserve. ReU represents one of the most important sites on the continent for migratory birds and emblematic species, such as the American bison, the black-tailed prairie dog, and the golden eagle. ReU is a key piece in maintaining the functionality of the binational biological corridor that connects the Great Plains in the United States with the Mexican highlands.
Thanks to a large multi-institutional effort in Mexico, progress has been made in the recovery of the American bison (Bison bison) in the wild. In 2009, 23 bison were reintroduced into ReU from conservation herds in South Dakota, USA, and in 2018, when ReU went into FMCN stewardship, the herd numbered 230 individuals; today, it is 290, which requires correct handling to maintain the health and viability of the bison population. In November 2019, 19 bison were moved from ReU to the plains of Coahuila, in the El Carmen Natural Reserve, within the Maderas del Carmen Protected Area, in a coordinated effort between the National Commission of Protected Areas (CONANP, acronym in Spanish), the General Directorate of Wildlife of the Ministry of the Environment and Natural Resources (SEMARNAT, acronym in Spanish), CEMEX, AES Mexico and FMCN.
ReU is operated and managed by the Cuenca de Los Ojos organization (CLO), which has spent the last 40 years on the restoration and protection of Mexican grasslands in northeastern Sonora, in addition to having extensive experience in regenerative ranch management; an example of this is the nine properties under its custody in northeastern Sonora. The collaboration between CLO and FMCN for the conservation of ReU is formalized through a donation contract that is renewed every year.