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Stand on the left bank badlands of the Río Colorado delta and most of the time you see barren, dried cracked mud as far as the eye can see -from Sonora to Baja California. Look to the sea where tidal bores once sank ships and 10 m tides support uncharted mass meadows of the endemic saltgrass Distichlis palmeri-potentially one of the most important grain crops for the world. Go northward 60 to 100 km to the California/Arizona borderlands: You pass the Ciénega de Santa Clara, a re-constituted and endangered wastewater wetland-the largest wetland in the Sonoran Desert. Then mosaics of parched salt flats, impenetrable expanses of tamarisk, halophytic desertscrub, xeroriparian thickets, sparse desertscrub, abandoned farmlands and then rich green farmlands, endless irrigation canals leaking into new wetland floras, new towns, new cottonwood gallery forests, and borderland farms and villages swelling into mega-city air-conditioned sprawl and their high horticultural diversity. It's not the first time the delta has gone dry-what happened during the pre-historic 17-year intervals when the river flowed into the Salton Basin? What will happen if the tamarisk thickets are eliminated with biocontrol? What were the predicted 200 to 400 vascular plant species extirpated from the delta-borderlands since the Big Dams? Is there a flora anywhere else so dynamic and so endangered?
Working bi-nationally to conserve shared species of mutual concern to Mexico and the U.S. presents unique conservation opportunities and challenges. Sharing knowledge and resources among academic institutions, NGOs, government agencies, and individuals from both sides of the border significantly enhances our ability to conserve species throughout their ranges, across political boundaries. Many mechanisms to achieve cross-border conservation exist or may be developed, such as formation of and/or participation in cross-border working groups to develop and implement bi-national conservation strategies. Though cross-border species often share similar threats and conservation needs, bi-national conservation mechanisms must always take into consideration the political, legal, and social differences in each country. Challenges to cross-border conservation may arise from trying to understand and manage these differences. The focused and dedicated effort of concerned cross-border partners, however, can ultimately result in significant conservation of shared species.Steve Schoenig (presenting for Gina Darin) , CDFA - (Integrated Pest Control Branch & UC Davis - Dept of Plant Sciences ) Invasive Plants and Border Issues in Southern California
California is occupied by over 1,200 species of naturalized, non-native plants. Of these, at least 200 have been identified as invasive. Fewer than ten percent of invasive plants are recognized as serious threats, but these few have dramatically altered California's landscape. Invasive weeds, are an incredible threat to biodiversity, second only to outright habitat destruction. Buffelgrass (Pennisetum ciliare), a landscape transformer, carries fire through non-fire-adapted communities and displaces native species in the Sonoran Desert of Mexico and Arizona. These bad actors are being intentionally and unintentionally introduced into California from neighboring states and countries. Prevention is the solution to the problems caused by invasive weeds, and with that, education and awareness. Early detection and rapid response activities catch new invaders, which do slip past the borders. The state and county agricultural departments have a strong track record in detecting and eradicating invasive plants that had begun to establish within the state. However, with reduced programs, California needs all botanists to help with early detection.
Thankfully, awareness is on the rise. Government officials and land managers from Canada, the USA, and Mexico convene every other year during the Weeds Across Borders conference to discuss weed management, regulatory issues, and concerns about weed dispersal throughout North America. Nationally, the USDA-APHIS is considering regulations to limit plant introductions into the United States based on assessing invasiveness potential. At the state level, the CDFA Border Stations are increasing weed detection efforts. As for the counties, the state legislature is again funding Weed Management Areas. And locally, nurseries are voluntarily pulling problem plants from their shelves. Weeds do not respect political or geographical boundaries. Therefore, we must build partnerships across borders to prevent shared problems caused by invasive plants.
Astragalus peirsonii has been an exceptionally controversial species, in terms of species conservation. Initially believed to occur only at the Algodones Dunes in Imperial County, and near Borrego Springs, in San Diego County, California, it was later reported from several locations near Salton Sea, in the Yuma Dunes, Yuma County, Arizona, and discovered in the Gran Desierto, Sonora. We investigate phylogenetic relationships and population genetics of Peirson's milkvetch. We show that A. peirsonii and A. magdalenae display greater evolutionary divergence than any other species pair of subsection Proriferi, section Inflati. This corresponds with divergence in seed size (a key trait of Peirson's milkvetch) between Mexican and U.S. populations. We examine the consequences of these new systematic conclusions of conservation issues.
The Sonoran and Mojave deserts meet just north of the Whipple Mountains, which are situated in southeast San Bernardino County, California, along the Colorado River and adjacent to Arizona. Plant collections in the area yielded primarily California Sonoran plants, but also several Mojave and Arizona Sonoran plants. A fair number of these Arizona Sonoran plants collected were on the western margins of their ranges. Climate data suggest that summer rainfall is a limiting factor underlying the vegetation differences between the western and eastern portions of the Sonoran desert, and a reason why some common Arizona plants do not occur west of the Colorado River. However, several of these plants do range into California in the Whipple Mountains, creating a unique flora and making an important contribution to California's floristic diversity.
The Campo Kumeyaay Nation is one of twelve Kumeyaay nations and one of eighteen Indian Reservations in San Diego County. Tribal lands represent a significant portion of the undeveloped lands of the County. San Diego County is also home to more endangered species than any other county in the United States. Coupled with the increase in population of the last fifty years, the potential for transboundary conflict has increased dramatically.
For the people of the Campo Indian Reservation, development has been accompanied by broad efforts to improve wetland/riparian habitats. The multiple benefits of reasoned approaches to these habitats are increases in the availability of plants for traditional use, increases in the storage of groundwater and the increase in wetland habitat for areas under control of the tribe.
This presentation will discuss the basic history of the Kumeyaay and the evolution of tribal jurisdictional authority in the United States. It will discuss the fundamentals of groundwater quantification and water quality in the southeast region of San Diego County using both County methodology and Campo's empirical data. There will be discussion of the implementation of Campo's stratagem in the Diabold Creek drainage and other parts of the Reservation.
The presentation will discuss conflicts with existing State and County groundwater policies, and with water usage by individuals, agriculture and water companies. It will cover the long term effects of global warming on water supply and the industrialization of the Tecate region.
In conclusion, several recommendations for a broader strategy will be brought forward along with a summary of current efforts of the Campo people to work for mutually acceptable programs through local, national and international forums.
Plant collection activities in this region date back to the 1870s, but there remains a lack of reliable botanical information on species distributions and extant populations from which to make good conservation decisions. Current floristic knowledge is especially difficult to obtain for those rarer plant species that are distributed near or across the international border because private lands with locked gates abound and regulatory procedures and statuses are different between the USA and Mexico.
The ongoing San Diego County Plant Atlas project and a future binational, multidisciplinary natural history expedition to the region hope to improve our botanical knowledge of this border's rich and threatened flora.