In the last decades, the environment agenda has become, along with the economic and social ones, in one of the most important issues for the governments of the countries in the entire world. This is the result of the interest and claim of the society to attend the, every time, more sensible environment problems derived from the growth of the modern societies. The diseases related to the air, water and soil pollution, the biggest severity of meteorological phenomena and the depletion of many natural resources contributed, undoubtedly, to establish the necessity to consider the environment component in the development policies.

In Mexico, the necessity to attend the environment problems confronted the government with the worrying reality of the insufficiency of knowledge and information that may allow it to objectively evaluate the environment situation and the natural resources, as well as the factors that affect them and the result of the implemented actions to stop and revert its deterioration. In this context, one of the necessary steps to state government strategies and policies that bring together the economic development and the environment conservation is to have enough and reliable information.

The National System of Environment and Natural Resources Information (SNIARN) has been one of the actions the Secretariat of Environment and Natural Resources (Semarnat) has developed to have information to support the decisions made. This system integrates, in an organized manner, statistical and geographical information related to the environment and the natural resources of the country, as well as the integration and analysis products, such as the National System of Environment Indicators (SNIA) and the Reports about the situation of the environment, among others.

The 2012 edition of the Report of the Environmental Situation in Mexico is an integral work of the SNIARN: it gathers, integrates and analyzes a large amount of statistical and geographical information from its databases; it is organized in seven chapters that cover the principal factors that affect the environment as the description of the state the biotic and abiotic environment components have: population and environment, terrestrial ecosystems, soils, biodiversity, atmosphere (which includes the issues of air quality, climate change and the thinning of the ozone layer), water and waste.

In the first chapter, the demographic tendencies are analyzed, as well as the socioeconomic features of the national population placing it in a global context; it also includes an analysis of the existing relationship among the population, the economy, and the environment that allows examining the close relationship among these three components. In chapter two, the situation and the uses of the terrestrial ecosystems in the country are described; as well as the processes that cause the change of the land use (i. e. deforestation, vegetation degradation and their conversion towards agricultural uses). At the end of the chapter, the measures and government actions implemented for the conservation, sustainable use and recovery of the national terrestrial ecosystems are exposed.

The soil is the topic of chapter three. Besides a brief description of the soils and their existences in the country; the results of the existing national evaluations on the principal processes that degrade them are shown and some of the causal effects are examined. The final part of the chapter presents the desertification issue and some improvements in the soil management are also presented.

In the fourth chapter, the situation of the biodiversity in Mexico is reviewed, as well as its most important threats, both at the ecosystem level and at the species level. The importance of the environment services derived from the biodiversity is stated and, finally, the most important strategies developed to protect our great biological wealth.

The issues of the air quality, climate change and the thinning of the ozone layer are studied in chapter five. There is a description of the emissions of the pollutants into the atmosphere and their relationship with the air quality in the urban areas of the country that have monitoring stations. Two issues of global character are also touched: the climate change and the thinning of the stratospheric ozone layer; there is description, for both of them, of the causes, consequences and measures taken to face these global environment problems.

Chapter 6 approaches, in detail, the water situation in the country, both in terms of the availability and the quality of this vital resource. It is examined the coverage of the potable water and sewerage services, as well as the available infrastructure for the treatment of the waste waters. It is important to mention it has been included the environment perspective of the resource, in other words, the importance of the marine aquatic and continental ecosystems to guarantee the supply of the goods and environment services they produce, mainly, the one related to fisheries.

Finally, chapter seven approaches the problem of the urban solid waste, the ones of special management as well as the hazardous ones. The analysis is made considering in an integral form its life cycle, in other words, from their generation until their handling and the final disposition.

The description of the situation of the environment presented in the Report includes, as far as it has been possible, a retrospective vision with the purpose to place the reader in a wider temporal context. In the cases where it was thought it was relevant, it was also included information of the international context. In the same way, as it was done in previous reports, this has decided to keep a series of boxes, throughout the chapters, where more information about a particular issue is more deeply analyzed or provided. These boxes may be read independently from the principal text, without affecting the continuity of the reading because they are made to be reviewed by those readers who have particular interests.

In the Report, some of the statistics are presented in a synthetized way in the form of tables, figures and maps, which allow the reader to follow, confirm or complement what it was mentioned in the text. For the public interested in consulting the information more deeply, references have been added to the boxes of the Compendium of Environmental Statistics -highlighted in light blue- and to the indicators of the Key and Basic Set, whose key is highlighted on bold type letters, either as IB or IC, respectively, and accompanied by the SNIA logo (SNIA) in the margin of the paragraph where they are mentioned. The boxes and the indicators must be consulted in the attached compact disc, which includes, in addition to the html version of the Report, the Compendium of Environmental Statistics and the complete sets of the Basic and Key Indicators. It must also be mentioned that this and other products from the SNIARN may be consulted in the website of the Secretariat at www.semarnat.gob.mx/informacionambiental/Pages(sniam.aspx.

Behind this effort of compilation and integration of the available environmental information, it is the interest this work be useful so the authorities and the society in general have an integral vision of the environmental situation in Mexico. We are sure, as long as the society and the decision makers, have more and better information, will be able to implement measures that contribute not just to stop and restore the ecological deterioration the country suffers, but also to promote a sustainable management of the natural resources and to foster an environmental culture that contributes to the conservation of the nature. We hope the gathered information, both in the Report and the statistical database and the SNIARN indicators may be used as raw material by the scholars and people interested in the environmental issues to, after analyzing it, contribute with their ideas and proposals for the benefit of the environment in Mexico.

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