THREATS TO THE BIODIVERSITY

An important part of the planet ecosystems has been transformed or shows evident deterioration signs caused by the human activities. These changes have unavoidably affected the state of their biodiversity, especially in the last 50 years, when the intensity of such activities has increased placing many groups and species in truly serious situations (PNUMA, 2011). This has been the consequence of a bigger demand for space, food, fresh water and power required by modern societies. Nowadays, it is acknowledged that the principal threats to the biodiversity, both in Mexico and in the world, are the change of the land use (mainly promoted by the expansion of the urban and agricultural border), the infrastructure growth (i. e. for the construction of highways, power networks and dams), the forestal fires, the overexploitation of the natural resources, the introduction of invasive species, the pollution, the illegal use and, more recently, the global climate change. The following paragraphs are focused on the problems of the invasive species and the illegal trade, taking into consideration the land use, the infrastructure growth, the use of the resources (forest, mainly), the pollution and the forest fires are studied in other chapters of this work.

The impact of the invasive species has been considered in the last years as one of the main reasons for the biodiversity loss at a global level. The invasive species affect the native species flora and fauna by means of the competition, predation, disease transmission, habitat changes and changes in the ecosystem function. In particular circumstances, there may be hybridization with the native species, altering their genetic pool (Comité Asesor Nacional sobre Especies Invasoras, 2010) and, the most serious cases, cause a decrease in the biodiversity of the ecosystems at causing the extinction of their native species.

The introduction vias of the invasive species into the ecosystems (either in a natural, intentional or accidental way) may be: 1) the transportation-sector related ones (both by the transported objects and by the means of transportation themselves), which includes military equipment and vehicles, products used by the freight and shipping, transportation by companies that do touristic activities and the animal movement by reason of entertainment, among others; 2) the trade, for the animal or vegetable products for human consumption, the aquatic or terrestrial plants for agriculture, gardening, horticulture or research, among others; 3) other human activities such as deforestation, opening of highways, mining, change of the land use, biological control and the union of previously isolated water bodies; and 4) by natural phenomena such as water current, winds, extreme climatic phenomena (such as hurricanes and floods) and other natural means for which the species have the particular morphologic and behavior adaptations (Comité Asesor Nacional sobre Especies Invasoras, 2010).

In our country, the Conabio is in charge of the Information System about Invasive Species in Mexico (SIEIM), which lists the 357 invasive species established in the country, most of them are plants (48% out of the total, in other words, 173 species), and fish (18%, 63 species); the list has also identified 10 species of amphibians and reptiles, six of birds and 18 of mammals as established invasive species. In general, such species are classified as high risk and high priority ones for Mexico (Conabio, 2012).  As part of the efforts to fight this problem, in 2010, the Conabio, in collaboration with several sectors, institutions, experts and civil organizations, published the National strategy about Invasive Species in Mexico, which, in addition to providing a diagnosis about the national situation about these problems, it establishes the priority actions which involve both the government and the civil society to face the situation.

The illegal use of wildlife specimens is one activity that threatens the biodiversity. In addition to the illegal hunting, the illegal use also includes the trapping, collection, transportation and not authorized trade of wildlife specimens. At the level of the populations of affected species, the principal consequences for this activity are the alterations in the population size and structures, in the relative number of females and males, in their reproductive potential and characteristics, in their genetic composition and in the repercussions in the flow and dynamics of the food chain of the communities they are a part of.

It is estimated that the illegal use of the biodiversity generates earnings that globally, may reach 20 billion dollars a year, with serious impacts for the ecosystems and the economy of many countries (Jolon, 2008). As a result of the actions to fight this activity in Mexico, between 2001 and 2011, the Federal Attorney Office for the Environmental Protection (Profepa) carried out the seizure of 28,266 wildlife specimens (Figure 4.4). It is important to note that this data only shows the minimum detectable trafficking, because it is very difficult to know the real total volume of specimens illegally trafficked inside and outside the country borders.

Endangered species

The threats mentioned in the previous section have contributed, in a high or low degree, by themselves or synergistically acting, to the reduction of the size of populations of several species in the natural ecosystems and to increase of the possibility of their extinction. The species with restricted distribution areas are the ones which are particularly vulnerable (for instance, the ones which are limited to surfaces relatively reduced to specific environmental conditions or the ones that live in islands or particular water bodies), the ones that, in a natural way, have small population sizes or those ones that have life cycles particularly longs or sensitive to environment changes.

In Mexico, the NOM-059-SEMARNAT-2010 is the standard that lists the species and sub species of wildlife flora and fauna which are endangered in the country². According to it, the number of listed species in any endangered category is 2,486³. The plants are the taxonomic group with the highest number of endangered species, with a total of 948. The families with the largest number of endangered species are the cacti (244 species, equivalent to 23.6% of the total of the species of this family described for the country), the orchids (188 species, 16.2%), the palms (64 species, 51.6%) and the agaves (39 species, 13.7%). In the case for the animals, the groups with more endangered species are the reptiles (437 species, in other words, 54.4% of the known species in the country for this), the birds (367, 33.5%), the mammals (242, 45.2%), the amphibians (194, 53.7%) and the fish (203, 7.5%; IB 6.4-3). According to such standard, the total of species probable extinct in the wildlife adds to 46 (18 birds, 13 fish, 9 mammals and 6 plant species). In the Figure 4.5, it is observed the distribution of the endangered species for each taxonomic group according to the categories used in the NOM-059-SEMARNAT-2010 (see also the Box The Red List of the International Union for Conservation of Nature).

Notes:

² In order to include, change or exclude any species of the standard, the Semarnat takes into consideration criteria that goes from the rarity, the taxonomic and ecological relevance of the species, until the total surface of their distribution area and the importance of the actual and potential factors which may affect their population sizes and their habitat, among other criteria.