Opuntia in México: identifying priority areas for conserving biodiversity in a multi-use landscape

Abstract

Background: México is one of the world's centers of species diversity (richness) for Opuntia cacti. Yet, in spite of their economic and ecological importance, Opuntia species remain poorly studied and protected in México. Many of the species are sparsely but widely distributed across the landscape and are subject to a variety of human uses, so devising implementable conservation plans for them presents formidable difficulties. Multi-criteria analysis can be used to design a spatially coherent conservation area network while permitting sustainable human usage.

Methods and findings: Species distribution models were created for 60 Opuntia species using MaxEnt. Targets of representation within conservation area networks were assigned at 100% for the geographically rarest species and 10% for the most common ones. Three different conservation plans were developed to represent the species within these networks using total area, shape, and connectivity as relevant criteria. Multi-criteria analysis and a metaheuristic adaptive tabu search algorithm were used to search for optimal solutions. The plans were built on the existing protected areas of México and prioritized additional areas for management for the persistence of Opuntia species. All plans required around one-third of México's total area to be prioritized for attention for Opuntia conservation, underscoring the implausibility of Opuntia conservation through traditional land reservation. Tabu search turned out to be both computationally tractable and easily implementable for search problems of this kind.

Conclusions: Opuntia conservation in México require the management of large areas of land for multiple uses. The multi-criteria analyses identified priority areas and organized them in large contiguous blocks that can be effectively managed. A high level of connectivity was established among the prioritized areas resulting in the enhancement of possible modes of plant dispersal as well as only a small number of blocks that would be recommended for conservation management.

Figure 1. Opuntia Records in México.

The existing protected areas are shown in gray. The red dots show the sites from which Opuntia occurrence records were available. The states that are named are those that are mentioned later in the Discussion.

Figure 2. The predicted distribution of Opuntia chaffeyi in México.

This distribution model was created using only four records and, accordingly, shows a highly restricted range. Darker areas have higher predicted habitat suitability.

Figure 3.Distribution. Distribution of representation targets.

A large number of species have high percentage targets indicating highly restricted ranges.

Figure 4. Plan A. The existing protected areas are shown in black.

The additional selected areas are in gray.

Figure 5. Plan B. The existing protected areas are shown in black.

The additional selected areas are in gray.

Figure 6. Plan C. The existing protected areas are shown in black.

The additional selected areas are in gray.

Figure 7. Agricultural and forestry areas in the new prioritized cells under Plan C1.

These are shown in red when they intersect with the new prioritized areas (that is, other than those in the existing protected areas). The solution corresponds to that in Figure 6.