Volume No. 10, 2001
Mexico is considered one of the most biodiverse countries in the world (Mittermeier 1988, Dinerstein et al. 1995, Instituto Nacional Indigenista 2001). Its territory of 1,953,162 km2, with 11,208 km of coasts, is nearly equally distributed above and below the Tropic of Cancer. The insular territory of Mexico comprises 371 islands, coral reefs, and kelp beds (CONABIO 1998).
There are 127 nature reserves, covering 7.8% of Mexico's continental land area, within the national system of natural protected areas (SINAP; CONABIO 2001). The distribution of these reserves does not represent the biological, geophysical, or political divisions of the country. For example, the states of Tamaulipas, Aguascalientes, and Guanajuato lack any federal nature reserves. As in the U.S., individual state governments can also establish and manage parks or protected areas.
The Mexican state of Nuevo Leon, located in the northeastern portion of the country, currently has 23 state and three federal nature reserves that cover approximately 4.4% of its land area. The state of Tamaulipas, located east of Nuevo Leon, has no federal nature reserves but five state nature reserves covering approximately 2.8% of its land area.
The National Commission for Knowledge and Use of Biodiversity (CONABIO) identified conservation priorities for Mexico based on the biological characteristics of specific areas, recognizing 151 terrestrial and 70 marine regions throughout the country as priority areas for the protection of biodiversity (Arriaga et al. 2000). Twelve areas were proposed for Nuevo Leon. If established as reserves, the proportion of protected lands in that state would exceed 23%. CONABIO proposed 13 terrestrial and 5 marine reserves for Tamaulipas; if established, these new reserves would increase the proportion of terrestrial protected areas in that state to 23.7%.
Efforts to identify gaps in networks of nature reserves have been conducted using biological features (Scott et al. 1993) as well as enduring physical features (Hunter et al. 1988). Cantú et al. (2001a, 2001b, 2001c) used both approaches in an assessment of the adequacy of existing and proposed nature reserves to capture the variation in elevation, climate, physiography, floristic divisions, potential vegetation types, mammalian, reptilian, and amphibian faunal provinces, and land use. This assessment was conducted for the entire country of Mexico and in more detail for the states of Nuevo Leon and Tamaulipas. This article briefly reports the results of that assessment.
This assessment was done using the best available data for Mexico as a whole and Nuevo Leon and Tamaulipas in particular. These data are both spatially and thematically coarse, and the effort is intended to show how the Gap Analysis method of identifying gaps in biodiversity conservation lands may be applied in Mexico as well as individual states of Mexico if spatial data of actual dominant vegetation types and each vertebrate species were available. The analyses presented here show the general level to which categories of elevation, physiography, potential vegetation types, faunal realms, and land use are represented in existing and proposed natural reserves and only indirectly provide a sense of the degree to which the overall biodiversity of Mexico, Nuevo Leon, and Tamaulipas is represented in these areas.
Digital maps of the proposed reserves (Cantรบ et al. 2002a, 2002b,2002c) and elevation (INEGI et al. 1990), climate types (García and CONABIO 1998), soil types (INEGI et al. 1991), physiography (Cervantes-Zamora et al. 1990), floristic divisions (Rzedowski and Reyna-Trujillo 1990), potential vegetation types (Rzedowski 1990), mammalian, reptilian, and amphibian faunal provinces (Ramírez-Pulido and Castro-Campillo 1990, Casas Andreu and Reyna Trujillo 1990), and land use and land cover for 1973 and 1996 (INE and INEGI 1996, CONABIO 1999), as well the boundaries of proposed terrestrial reserves, were obtained from the CONABIO web site (www.conabio.gob.mx). The boundaries of the existing nature reserves were provided by the National Commission of Natural Protected Areas (SEMARNAT) and the state governments of Nuevo Leon and Tamaulipas.
All of the data sets were combined and analyzed using ARC/INFO version 8.02 and ArcView version 3.2 software. Differences in map scales and map projections for the various data sets caused the area estimates calculated for the different categories to vary. However, considering the broad scale of the analysis, we did not consider these differences to be meaningful.
For the purposes of this analysis it was assumed that any resource category with less than 12% of its area in protected areas was underrepresented. We chose 12% because that percentage has been suggested in the past as a conservation target for entire nations (Bruntland 1987, IUCN 1992). However, it has not been proposed as a conservation target for particular resource categories, and we do not suggest that this figure has any established scientific validity.
We found that the 127 existing federal reserves, when combined with the additions proposed by CONABIO, would place 29% of Mexico's land area in nature reserves. The existing reserves adequately protected (i.e., > 12%) only those lands with elevations > 3000 m (which represent < 1% of the country). Adding the reserves proposed by CONABIO results in all elevation zones, climatic divisions, and physiographic provinces having at least 12% of their lands in protected areas. With the existing set of reserves, the analysis of 1973 land cover data indicated that nine of the 23 potential vegetation types exceed the 12% standard in the current nature reserves. Under the "existing and proposed" reserve scenario, all 23 of the potential vegetation types would be protected. Under the existing nature reserves scenario, oak forest, pine forest, cloud forest, chaparral, savanna, three types of tropical forest and five types of xeric scrubs are underrepresented. All categories exceed the 12% threshold in the current and proposed nature reserves, and 14 categories have 30% or more of their area in current and proposed nature reserves.
Despite the increased protection of biological and geophysical features provided by the proposed CONABIO reserves, gaps remained when the analysis was conducted at the state level. For Tamaulipas, we found that most of the existing protected sites occur in areas with elevations > 1,000 m. These are in temperate climates and are dominated by pine forest, oak forest, and cloud forest cover types. The state's dominant physiographic region-low-elevation coastal plain with tropical and arid climate types and xeric scrub vegetation-is disproportionately underrepresented in the current reserve system. If the new protected areas were established, the largest gap would be in the low-elevation, level, coastal lands. For example, for the five xeric scrub types that cover 35% of Tamaulipas, less than 1% of their area is represented in current nature reserves. With the addition of CONABIO's proposed areas, four of the five types remain underrepresented.
For Nuevo Leon, we found that the existing reserves are located primarily in regions with elevations between 1,000 and 1,500 m, slopes greater than 45%, and soils of low productivity (Litosols), with a temperate climate, and dominated by pine and oak forest cover types. The state's dominant physiographic region-low-elevation coastal plain with arid climate types and xeric scrub vegetation-is disproportionately underrepresented in the current reserve system. If the new protected lands were established, the largest gap would be in the low-elevation, level, coastal lands with xeric scrub communities.
The nature reserve areas proposed by CONABIO would greatly increase the protection of geographical features in Mexico and the states of Nuevo Leon and Tamaulipas. Whether this would also result in an increased protection of biodiversity remains unknown, as adequate maps of species distribution and detailed actual vegetation types are not available. However, gaps in the protective network would remain, particularly at the state level. Furthermore, establishment of additional nature reserve areas along without sufficient funding to manage and protect them will not insure the long-term survival of these features and the species that reside in them.
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