In the legal framework of urban planning in Mexico, the provision of urban green areas is approached from a social perspective, as public spaces for recreation and sports activities, regardless of the environmental and economic benefits they can provide from a sustainable development perspective. The planning of urban green areas requires a set of conditions in order to be successful, among which are: an updated regulatory framework, adequate financial resources, technical knowledge of the appropriate plant species and the effective participation of the community. However, without a complete and classified inventory of the existing green areas, any planning is unfeasible. Therefore, this paper presents the first stage of the study of urban green areas in a city of the State of Baja California, Mexico, developing firstly, a review of the regulatory framework and a redefinition of the concept of urban green areas that takes into account the basic dimensions of sustainability, and on the other hand, it proposes a general classification of urban green areas that includes all types of open spaces with vegetation: both for public and private use, subdivided into systems and subsystems, which were the basis for the identification, classification and quantification of urban green areas, using Quickbird multispectral images of 2.6 m resolution and applying the Normalized Difference Vegetation Index (NDVI) using IDRISI software, and data were integrated in a GIS; finally, the results and discussion are presented.

The urban-rural interface has usually been studied from the point of view of cities with different sectoral interests and very little from rural perspectives. Nevertheless, these kinds of areas need to be studied from both points of view and from comprehensive approaches that could reflect their complexity. Thus the work is oriented to make a comparative analysis of two main approaches to dealing with the rural-urban interface in a Latin-American context: one coming from towns and the other from the countryside, where both of them include the sustainable and a territorial perspective of development. The analysis has taken into account economic, social, environmental and political-institutional issues, as well as urban-rural interactions. Results underline some contributions of such approaches to theory and practice of planning and management of these spaces; such as the value of a complex systems view, planning in different spatial scales and time scenarios, the territory as a support of socio-economic and environmental processes and the role of local actors in this transformation. To conclude, rural development has been arising as an emergent field where medium and small size towns play an important role in linking production with local and global markets and enforcing rural-urban relationships in urban systems.

Human settlements worldwide have experienced environmental problems as a result of population growth, an increase in productive activities and low financial capacity of municipalities to provide adequate infrastructure and public services. At the local level, problems of water, soil and air pollution, as well as, land use changes have arisen due to the expansion of urban agglomerations. Regionally, there have been negative impacts on watersheds, ecosystems and biodiversity. Globally, the world is experiencing climate change, the reduction of the ozone layer and the increase of natural disasters. The situation has posed a challenge in terms of urban and regional planning, especially for metropolitan areas and medium-sized cities. The purpose of this study is to present an alternative to integrate environmental sustainability into metropolitan planning in Mexico, specifically applied to the Metropolitan Area of Mexicali, Baja California. Therefore the Environmental Sustainability Agenda has focused on three objectives: first, identifying the weaknesses of the existing environmental and human settlements legal framework; second, developing an environmental assessment and; third, designing policies, strategies and indicators to implement institutional monitoring of environmental programmes. The results were obtained by conducting surveys, regional community workshops, and reviewing previous research. Lastly, this study concludes with six sectoral programs: water, air, solid wastes, green areas, soils and physical pollution and six transversal Sustainable Development and Planning VI 267programs that have effects on environmental education, health, climate change, environmental management and the legal framework.

Urban development planning in Mexico begins with the publication of the General Law on Human Settlements in 1976, which sets up several planning instruments to regulate land use and urban development at state, municipal and urban level. Urban planning in the late seventies was characterized by being made by the state, with a rational approach, enforced from a top-down perspective, supported by planning guides made by professional planners and public consultation at the end of plan making. Current urban planning has been modifying its methods to a strategic and communicative model, a bottom-up perspective. The state has been playing a regulatory function and the participation of stakeholders has become a central issue on urban development planning and management. Therefore, this study has two main purposes: firstly, to analyse the evolution of urban planning in more than four decades and; secondly, to present Mexicali city as a good practice case study of the application of the bottom-up planning model. This project shows the changes that urban development has undertaken throughout a strategic planning view, oriented to long term perspective, organized and undertaken by society with collaborative work coming from different sectors: government, private and nongovernmental organizations. The methodology was based on the Logical Framework Approach, working along nine months with thematic groups. The results were integrated in a project portfolio, to be implemented in the short, middle and long term. Lastly, findings show successes in urban development planning and obstacles that society has faced in order to implement development projects within a political municipal agenda.

Mexicali has an important economic role within the state of Baja California, Mexico, and its urban economic dynamic has been a central piece of regional development in the Mexicali valley. This has produced a rapid urbanization of the rural-urban interface, which has intensified energy, material and population exchanges between the central city and its hinterlands. Such a dynamic has produced urban sprawl and a fast restructuring of the urban regional spatial development. Thus, the purpose of this paper is to analyze the spatial dynamics of the rural-urban interface of Mexicali, from 1990Mexicali, from -2005. Urban spatial expansion was analyzed by satellite images, LANDSAT TM5 and LANDSAT ETM7 taken in the dry season, to identify land use changes and the physical expansion of the urban area over the last 15 years. Results have showed that Mexicali's urban area has expanded by around 32 km 2 , which means an increase of 34% during this period. Meanwhile small cities located in the hinterlands have experienced lower rates of population growth and physical expansion. Some small cities have been absorbed and others have developed over urban corridors to the central city. Changes in spatial patterns of urban structure have been accompanied by the evolution of urban functions and special interactions between the central city and its hinterlands. Lastly, the urbanization process is still in progress, but there are also evidences of urban sprawl in the hinterlands.