In 1966, the endangered list consisted chiefly of birds and mammals (warm-blooded vertebrates), but, now the list contains of plants and invertebrates as well (ESA, Website_1; Chadwick, 1995). Habitat destruction and loss highly affects the breeding ranges of birds in particular, but also largely contributes to general degradation of the biodiversity of an area, threatening multiple species. In 1995, the Center for Plant Conservation stated that 4,000 (20%) plant species in the U.S. are imperiled and perhaps 700 could be gone by 2005 (CPC, website_1). In the Colorado River delta, there are two types of marshes containing important plants: (i) a cattail (Typha domengensis)) brackish marsh called the Cienega de Santa Clara and (ii) an intertidal, salt marsh with endemic saltgrass (Distichlis palmeri) (Glenn et al., 1992a, 1992b; Glenn et al., 1996; Zengal et al., 1995)). In these marshes a diversity of other plants is supported, including the water pennywort (Hydrocotyle verticillata) and flat sedge (Cyperus laevigatus) (Glenn et al., 1992a, 1992b; Glenn et al., 1996; Zengal et al., 1995).

   Along with endangered plants, invertebrate species have been listed by ESA. Freshwater mussels are important for the natural ecosystem; they are a good indicator species for detecting water quality problems. They are a shelter for micro-organisms and are a food source for fish, birds, waterfowl, and small vertebrates. The shells are also economically viable, as they did once provide buttons at a time when shells, not plastics, were used. Additionally, they are medically viable, as the shells are being explored by medical researchers due to their resistance to tumors. However, in the U.S. alone, approximately 60 of 300 freshwater mussels are listed as endangered. As 75 or more species are currently declining, this has severe implications for the species that feed off them and use them as protection, as well as for the medical treatment of humans (Chadwick, 1995).

   Similar to mussels, clams are also an important indicator of ecosystem health. A press release detailing the findings of a scientific study "Taxonomic status and distribution of the bivalve mollusk Mulinia coloradoensis in the Gulf of California (Flessa and Tellez-Duarte, 2001)" concludes that a clam found at the mouth of the Colorado River in Mexico occurs nowhere else in the world. A related 1999 report by the Center for Biological Diversity (CBD) and Defenders of Wildlife (DoW) concluded that drastically reduced Colorado River flows from the U.S. is the likely cause of the near extinction of the species (CBD, 2001).

   The preservation of the diversity of species is complex. The protection of large, vast wildlands would help to rectify the problem faced by the ESA. The National Parks system and public domains, such as state parks, are expected to carry out protection and recovery efforts. However, as the former Assistant Secretary of the Interior, Nathaniel Reed, stated, "it is only through the willing assistance of private landholders that ecosystem management may succeed" (Chadwick, 1995). This has been especially true in the Colorado River delta region where private landowners have applied for grants to use parts of their land and water rights for restoring riparian habitat for the endangered southwest willow flycatcher (Empidonax traillii extimus) (Briggs, M., 2001, pers.comm). Despite agricultural development along the delta, it is the U.S. politics that govern the distribution of the water, in addition to development in Mexico, that has contributed to habitat loss. The willow flycatcher and other endangered bird species in the delta need water, and a riparian vegetation corridor for breeding ground (Garcia-Hernandez, 2001).

   Development is rarely stopped by the ESA; of the 100,000 or so interagency consultations during a 5-year period, all but 55 project plans were modified (Chadwick, 1995). Wildlife managers and land-use planners work together to answer questions of how much space and financial support is needed to accomodate both species-protection and land-use planning. Both sides of the equation can be appeased through planning and ecosystem management: a small number of acre fragments of habitat, linked by a corridor, has been a successful solution in providing space to roam without consuming vast amounts of acreage to give protection (ESRI, 2001).

   Land-use planners use a geographic information system (GIS) and data from ecologists, biologists, and developers to superimpose maps of vegetation, rivers, drainage patterns, urban infrastructures, and each species' habitat extent and type. A GIS can include statistics relevant for determining which area is the most critical habitat for a particular species or group of species. Findings have shown that species-rich areas do not necessarily overlap with National Parks, but often do so with privately-owned land (ESRI, 2001). A GIS can help to identify where gaps are in protected areas and, help planners understand where the highest species' density in unprotected areas may be despite a fragmented landscape.