Estuaries are partially enclosed regions where large rivers enter the sea. They rank among the most productive of marine ecosystems as they typically contain a high biomass of benthic algae, sea grasses, and phytoplankton, and support large numbers of fish and birds (Lalli, Parsons, 1993). Humans have their most intimate contact with marine environments and their greatest impact in estuaries; both the value and vulnerability of estuaries are in their multiplicity of uses (Nordstrom, 1992). Understanding the value of the estuary as a natural reserve will provide a platform for improving the environmental conditions of the ecosystem, as well as the relation of the community that benefits from it. This paper will analyze the main features of a specific estuary situated in the Baja California peninsula, then discuss the actual development within and outside the ecosystem. It will also analyze the ideal approach of achieving the rehabilitation of the estuary while at the same time reviewing sustainable development by identifying priorities through an ecological assessment of the area.
San Jose del Cabo estuary (Source: CAPA Lab, 2010)
The riparian system of the Basin and the San Jose del Cabo estuary is formed by a diverse topography, which is made of the mountains of the Sierra de La Laguna to the west and the Sierra de la Trinidad in the east. The first range reaches maximum heights of about 1,900 m, the second features a maximum height of 700 m. Combined these form a watershed with a diamond-shaped skirt on both mountains. Towards the lower parts of the basin are observed active river valleys.
The climatic characteristics of the region derive primarily from its position
geographical south of the peninsula, which determines the incidence of three factors. The first is the high North Pacific subtropical pressures. The second factor is a series of phenomena that lead to conditions of dryness in the area. The final climatic input is the impact of tropical storms and cyclones. These storms define the predominance of summer rainfall. The intensity of these weather patters, and the California Current, cause a constant temperature inversion and rain, allowing the presence of winter rainfall.
The San Jose River (figure 1.) is one of the largest in the state of BCS. The San Jose River basin drains 1.235 km ‘with a length of 78.05 km and an average gradient of 1%. This extraordinary flow of water has an estimated maximum return period of 1, 000 years. According to the National Water Commission is 8,000 m3 / s. The hydrological characteristics of the region are defined by climate and topography, which generate torrential local schooners and ephemerals. In times of cyclones these can develop a large volume of water that fills the lower parts, which are reduced areas with a continuous flow, located in the main channels of the Sierra de La Laguna (northwest of the basin), which disappear when infiltrating the base of it. The San Jose station reported an average annual rainfall of 309.7 mm, with the months of August and September increased precipitation, with the lowest rainfall in March, April and May. The normal annual average temperature is 23.4 degrees Celsius, with a normal maximum of 29.5 degrees and can reach up to 40 degrees (November) and normal minimum of 17.2 degrees with peaks present in January and February (less than 10 degrees).
Figure 1 (Source: CAPA Lab, Gonzalo Elizarraras, 2009)
The vegetation is a mostly annual or perennial herb with a short life. The remaining vegetation is composed of perennial grasses, shrubs and tree seedlings (among them, are fan palms). This stage of succession can be considered as the stage of plant colonization by pioneer species that are established in the early stages of succession and are generally characterized by cycles of short life and rapid growth. However, the presence of palm seedlings and other shrubs typical of mature or stable vegetation, indicate that this model of succession in the area corresponds to what has been called a model of tolerance, where pioneer species cohabitate between late and early succession stages.
The estuary of San José has a community of terrestrial and aquatic birds that are exclusive to the southern region of the peninsula. The bird community is composed of resident species and migratory. It is the last rest station for waterfowl and shorebirds migrating to areas of southern Mexico, Central or South America. Currently the area has been altered, and there have been drastic changes in the composition. Part of the fauna present in the estuary includes several species of reptiles, amphibians and mammals, and in some cases the species are endemic. There are several ecosystems in the southern part of the Baja California peninsula, such as Cabo Pulmo (marine reserve), Todos Santos and Sierra la Laguna, among others, which are contributing to the environmental balance in the region. From an ecological perspective the estuary plays a major role in the general landscape, since it is positioned in the last stage of the hydrological system, linking both the terrestrial and aquatic environment.
The Coastal zones and estuarine habitats are among the most productive ecosystems on Earth. In many locations they are subjected to a variety of anthropogenic stressors, such as pollution and eutrophication (Duarte, Vieira, 2009). Because most estuaries and coastal lagoons are transitional areas they receive large amounts of nutrient and pollutant inputs derived from urban, agricultural and industrial effluents (Duarte, Vieira, 2009). The lenthic condition of the estuary enhances the process of eutrophication through two processes, one of inorganic nutrient surface drainage into groundwater and another of high human activity. For example, the discharge of untreated urban wastewater accelerates the eutrophication process, which is unfavorable for the maintenance of the aquatic characteristics of these environments. As of lately, the increment of land use has declined the vitality of the estuary. This is caused by real estate development which affects (both directly and indirectly) illegal harvesting of palm through complete extraction, and irregular construction of facilities within the reserve. The urban wastewater from the city of San Jose del Cabo is the main source of effluent that contaminates the stream and the estuary. It is possible to improve the features of the effluent before being discharged into the streams through phytoremediation, therefore rehabilitating the ecosystem. This could be achieved by constructing a system composed of aquatic plants and several substrates (gravel), which decompose the organic material and remove the pollutants within the effluent through the combined action of physical, chemical and biological processes. The warm conditions of the climate in the region are essential for its performance.
The estuary as a public park: Involving the community.
It has become increasingly important to incorporate the dynamic interactions between societies and natural systems (Berkes, 2003). Humans are a part of the ecosystems, therefore natural preservation of the ecosystem, as well as human development, must converge in a sustainable balance. This balance requires interdisciplinary organization including the government and stakeholders. Success may rest in partitioning (zoning) these systems into categories weighted towards human uses (the anthropocentric component) and/or towards the conservation and/or preservation of lesser disturbed systems, or parts thereof (Weinstein, 2008). The conservation of the estuary health and preventing deterioration and preserving the natural conditions of the environment are dependent on the economy, since a large part of the general income of the region comes from tourism.
Urban waters are especially sensitive to climatic extremes such as droughts and heavy precipitation, which can be exacerbated by the urban environment. Therefore the rehabilitation of degraded urban waters including the creation of wetlands will be more important in buffering adverse climatic impacts in the future (Schanze, Olfert, Tourbier, Gersdorf, Schwager, 2004). Besides ecological issues in urban areas there is also a cultural framework for water rehabilitation. This means that social, economic and aesthetic requirements also have to be considered (Schanze, Olfert, Tourbier, Gersdorf, Schwager, 2004). Envisioning a rehabilitation project of the estuary may require a programmatic plan of action with the aim of achieving a sustainable development and management of the ecological resources. The main scope of the zonification program is to identify the features of each area within the reserve, and set the primary priorities and zone uses (figure 2). The starting point of the rehabilitation plan would be the reclamation of zone II (figure 2) as a public park considering preservation, education and recreation as the main carrying factors.
Building knowledge and ecological relationships is the basis for putting humans back in the ecosystem (Berkes, 2003). The attributes of adapting the estuary as a public space are essential to reverse the negative impacts that have been slowly but constantly emerging in the last decades. The community would need an active stimulation in order to achieve a positive involvement with the ecosystem. This can be accomplished by experiencing the estuary from within. Incorporating humans back into the ecosystem requires using all possible sources of ecological knowledge and understanding as are available (Berkes, 2003). 11% of the reserve is destined for commercial and touristic use, and it could be sufficient to contribute to the pollution within the estuary. This is why the reserve needs an urgent regulation system that ensures sustainable development in the area. Only 5% of the reserve has been chosen as a research area to be developed as a recreational ecological park. This is the major component of involving the community, aiming for an integral social comprehension of the ecosystem. The streams and the estuary, as well as the entire reserve can be rehabilitated and therefore can become an ecological and social icon for the city. The population of San Jose del Cabo that benefits from the estuary includes the residents, tourists, scientists, academic researchers, entrepreneurs and developers, among others. These users are essential for achieving the estuary rehabilitation.
Figure 2 (Source: CAPA Lab, Marcos Cohen, 2009)
The reserve that contains the estuary is a determining ecosystem in the region, providing essential services to the community. The anthropogenic impacts that the ecosystem perceived in the last years had contributed to a rapid deterioration of the environment, harming different habitats where multiple and varied organisms live. The starting point of the rehabilitation process needs to start from the enhancement in the quality of the effluent discharged in the streams, since biodiversity depends on primary producers and these are threatened by pollution. With the passing of time and an active involvement of the community as well as the authorities and stakeholders, several areas within the ecosystem would be restored and other stages in the process of rehabilitation can be carried out. It is a fact that there is a potential opportunity for accomplishing a rehabilitation of one the most unique, rich and diverse water ecosystems in Mexico.
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