|
|
  | |
|
Biodiversity Significance of the wildlands and parks 
Global Significance The ecosystems of The Irvine Ranch wildlands and parks are part of the California coastal sage and chaparral ecoregion, a biogeographic unit within the California Mediterranean-climate Province (Dallman 1998, Cowling et al. 1999, Olson et al. 2001, Myers et al. 2000). Mediterranean-climate ecosystems, wherever they occur, represent a global conservation priority as they are home to an extraordinary concentration of unique plant and animal species and all are under great threat. Indeed, habitat conversion has been extensive and exceeds habitat protection by 8:1 in the Mediterranean biome, making it one of the most endangered biomes on the planet (Hoekstra et al. 2005) and a hotspot for species extinction. Mediterranean-climate ecosystems are characterized by warm, dry summers and cool, wet winters. Although the five Mediterranean-climate areas that make up this biome occupy less than 5% of the Earth's surface, they support roughly 48,000 known vascular plant species, almost 20% of the world total. Some biogeographers consider large areas of Central Asia to experience Mediterranean-climate conditions, as well, which would expand the flora to around 75,000 species. Mediterranean floras are notable for very high levels of endemism (species found only in one place), including a large number of restricted-range species (species with very small distributions) (Cowling et al. 1996, Myers et al. 2000). 
Significance within the California Hotspot The Santa Ana Mountains and associated coastal ranges are one of the very last places where relatively large blocks of intact lowland habitats characteristic of Southern California occur. Throughout California, the vast majority of the coastal sage scrub (less than 10% remains and few, larger blocks persist), native grasslands (less than 1% remains intact), and other lowland habitats have been converted for development and agriculture, endangering a suite of habitat-specific species, such as California gnatcatchers (Polioptila californica californica), Cactus wren (Campylorhynchus brunneicapillus sandiegensis), Pacific pocket mouse (Perognathus longimembris pacificus), and thread-leaved brodiaea (Brodiaea filifolia). For these reasons, The Irvine Ranch wildlands and parks constitutes a globally outstanding conservation priority. The North Ranch portion of the wildlands and parks is contiguous with the Cleveland National Forest and represents one of the very few places where natural habitat ranges unbroken from lowland scrub, grassland, and oak woodlands up to the montane chaparral and conifers of the Peninsular Mountains. The Venturan and Diegan forms of California coastal sage scrub and native grasslands of Southern California are all critically endangered and the Ranch offers one of the last, best places to conserve these distinct ecosystems and many of the species that are closely associated with them. The land is also sufficiently large and connected to nearby wildlands to support native ecosystems that still benefit from the presence of larger predators, such as cougar, coyote, golden eagle, and bobcat. Their role as top predators helps maintain healthy and resilient ecosystems. The Ranch wildland's habitats represent some of the last and most extensive lower elevation habitats for bobcats, cougar, and coyotes to inhabit in the region. For all of those reasons, much of the open space on The Irvine Ranch wildlands and parks has been identified by the Nature Conservancy as one of the top 50 priority conservation landscapes within California. The natural areas are adjacent to one of the world's largest urban areas and offer an opportunity for people to experience and enjoy these extraordinary native ecosystems in their backyard and enhance their understanding and support for conservation. The large area of land, the strong commitment to long-term stewardship, and the quality, professionalism, and resources of the conservation community and natural resource managers here also offer an exceptional opportunity to test innovative approaches for restoring native Mediterranean-climate ecosystems. Literature Cited Cowling, RM, PW Rundel, BB Lamont, MK Arroyo, and M Arianoutsou. 1996. Plant diversity in Mediterranean-climate regions.Trends in Ecology & Evolution 11:362-366. Dallman, PR. 1998. Plant life in the World's Mediterranean climates. California Native Plant Society, UC Berkeley, Berkeley, California. Hoekstra, JM, TM Boucher, TH Ricketts, C Roberts. 2005. Confronting a biome crisis: Global disparities of habitat loss and protection. Ecology Letters 8:23-29. Myers, N, RA Mittermeier, CG Mittermeier, GAB da Fonseca, and J Kent. 2000. Biodiversity hotspots for conservation priorities.Nature 403:853-858. Olson, DM, E Dinerstein, ED Wikramanayake, ND Burgess, GVN Powell, EC Underwood, JA D'Amico, HE Strand, JC Morrison, CJ Loucks, TF Allnutt, JF Lamoreux, TH Ricketts, I Itoua, WW Wettengel, Y Kura, P Hedao, and K Kassem. 2001. Terrestrial ecoregions of the world: A new map of life on Earth. BioScience 51:933-938. Mediterranean-Climate forests, woodlands, and shrub ecoregions around the World (Olson et al. 2001) Nearctic Mediterranean forests, woodlands, and shrub California chaparral and woodlands Mexico, United States California interior chaparral and woodlands United States California Central Valley grasslands United States California montane chaparral and woodlands United States, Mexico California coastal sage and chaparral United States, Mexico Northern California coastal forests United States Neotropic Mediterranean forests, woodlands, and shrub Chilean Matorral Chile Chilean Valdivian forests Chile, Argentina Afrotropic Mediterranean forests, woodlands, and shrub Albany thickets South Africa Lowland fynbos and renosterveld South Africa Montane fynbos and renosterveld South Africa Australasia Mediterranean forests, woodlands, and shrub Coolgardie woodlands Australia Esperance mallee Australia Eyre and York mallee Australia Jarrah-Karri forest and shrublands Australia Kwongan heathlands Australia Mount Lofty woodlands Australia Murray-Darling woodlands and mallee Australia Naracoorte woodlands Australia Southwest Australia savanna Australia Southwest Australia woodlands Australia Palearctic Mediterranean forests, woodlands, and shrub Aegean and Western Turkey sclerophyllous and mixed forests Greece, Macedonia, Turkey Anatolian conifer and deciduous mixed forests Turkey Canary Islands dry woodlands and forests Spain Corsican montane broadleaf and mixed forests France Crete Mediterranean forests Greece Cyprus Mediterranean forests Cyprus Eastern Mediterranean conifer-sclerophyllous-broadleaf forests Israel, Jordan, Syria, Turkey Iberian conifer forests Portugal,Spain Iberian sclerophyllous and semi-deciduous forests Illyrian deciduous forests Albania, Bosnia and Herzegovina, Croatia, Greece, Italy, Slovenia Italian sclerophyllous and semi-deciduous forests France, Italy Mediterranean acacia-argania dry woodlands and succulent thickets Morocco, Canary Islands (Spain) Mediterranean dry woodlands and steppe Algeria, Egypt, Libya, Morocco, Tunisia Mediterranean woodlands and forests Algeria, Morocco, Tunisia Northeastern Spain and Southern France Mediterranean forests France, Spain Northwest Iberian montane forests Portugal, Spain Pindus Mountains mixed forests Albania, Greece, Macedonia South Appenine mixed montane forests Italy Southeastern Iberian shrubs and woodlands Spain Southern Anatolian montane conifer and deciduous forests Israel, Jordan, Syria, Turkey Southwest Iberian Mediterranean sclerophyllous and mixed forests France, Italy, Morocco, Portugal, Spain Tyrrhenian-Adriatic sclerophyllous and mixed forests France, Spain |
|
|
