Riparian ecosystems are among the most impacted by human activities despite their great importance as refuges for biodiversity and providers of environmental services. The Nazas River is one of the most important wetlands in north-central Mexico. This river boosted the development of La Comarca Lagunera, a region of great economic importance to the country. However, regional development has led to the deterioration of this vital socio-ecosystem and its services. Despite these efforts, no studies have integrated multiple indicators to comprehensively assess the overall health of the basin. Instead, previous research has largely relied on isolated indicators. For this reason, this study prioritized an initial health assessment of the Nazas River, considering three main indicators: a biological indicator based on the fish community, a physicochemical indicator of water quality, and a physical indicator of the condition of the territory surrounding the river. The study found a marked gradient in overall health, ranging from the least degraded in the upper reaches (0.76 Ramos River and 0.68 Sextín River) of the river to the most degraded in the lower reaches (0.63 Lower Nazas), and highlighted the Peñón Blanco River in the middle section as a priority area for conservation and a possible biodiversity refuge due the Comprehensive Health Assessment 0.80.

Castor bean plants yield commercially important oilseeds with multiple uses; they are characterised by tolerance to drought and adaptation to marginal soils in arid and semi-arid regions. In northern Mexico, a large amount of arid land is categorised as “ejidos”: a system of mixed land ownership managed under a specific legal system, where land users have access to common or individual (parcelled) land. This work aimed to examine the suitability of castor bean cultivation on unused marginal land in ejido land. To determine the environmental suitability of the ejido lands of Coahuila, Mexico, we adapted a land Productivity Index (PI) from an existing method; it consisted of a set of biophysical indicators (edaphic factors, climate, and topography) adapted to castor bean cultivation. We then complemented this index with a “cultural component”, assessing the ethnobotanical knowledge of the people, their willingness to implement a new crop type, and the type and current use of the land. As a result, we found that 114,300 ha of ejido land (1.76% of the total) were very suitable for castor bean cultivation according to the Environmental-PI and that 808,524 ha of ejido land (12.4% of the total) was very suitable according to the Cultural-PI. We also hypothesised that the willingness of “ejidatarios” to cultivate castor beans was related to their degree of knowledge about the plant and the land available for its cultivation; however, their willingness was mostly related to differences in land tenure: “ejidatarios” who own parcelled land were more interested in obtaining benefits from the land through the implementation of novel crops, compared to those who only have access to common land. Highlights • In Mexico, the “ejido” is a unique land ownership and management system where users have access to common or individual (parcelled) land. • According to our Environmental Productivity Index, 114,300 ha of ejido land in Coahuila, México, were very suitable for castor bean cultivation. • This index was complemented with a “cultural component” gauging the people’s perception and willingness to introduce castor bean as a new crop. • 808,524 ha (12.4%) of ejido land were very suitable for castor bean cultivation according to the cultural component of our index. • Differences in land tenure most strongly influence the willingness of the ejido people to cultivate castor beans.