Saving the endemic and endangered flora of Baja California
Michael Way describes the importance of an integrated plant conservation strategy for the Baja California peninsula in Mexico.
For many visitors, the Baja California peninsula and the Sea of Cortés are renowned for their rich marine wildlife, providing the chance to encounter sea lions and the grey whales that breed in these warm waters each winter. So how do the terrestrial habitats compare?
Actually the 1,200km length of the Baja California peninsula is remarkably varied in geology, climate, and landform, and may support as many as 4,000 native plant taxa, many of which are still the focus of botanical exploration.
This research is vital because some of the ecosystems of the region are under continuing threat: for example the development of housing and vineyards in the north of the peninsula, and expansion of coastal resorts in the south, could affect the habitat of species not yet fully evaluated for conservation. As part of the Millennium Seed Bank Partnership, Kew cooperates with local botanists to urgently safeguard seed from these endemic and threatened plants.
Why is the plant diversity of Baja California so precious?
The starting point is an array of igneous rocks which forms a spine along the length of the peninsula, and these formations are complemented by a range of sedimentary and metamorphic rocks that provide a diversity of soil conditions and opportunities for specialised plants. Interestingly, at the shoreline it appears that the extensive shell deposits left from shellfish harvesting by indigenous communities have added a strong calcareous influence, as well as contributing to local flora diversity.
The peninsula extends across ten degrees of latitude, (comparable to the distance from London to Madrid), and spans temperate and tropical climates with contrasting temperature and rainfall regimes. Either side of the US border, the Californian Floristic Province (with Mediterranean climate, and winter rainfall) encompasses one forest type and several shrub communities. The mid zone of the peninsula, centred on the massive Vizcaino Desert, has a Sonoran desert climate. Further south, the Cape receives summer rain storms more typical of the tropics. In combination, 13 ecological regions have been delimited (Rebman & Roberts, 2012) and it is possible that the adjacent cool and stable Pacific Ocean may have facilitated speciation by extending the growth and flowering season for native plants (Vanderplank & Excurra, 2015).
How much progress has been made so far in protecting the flora?
As development has expanded in recent decades, so has the determination of local biologists to preserve and protect key wildlife habitats for future generations to value and enjoy. Some fifteen areas have been given formal protection by Federal government (Excurra in Rebman & Roberts, 2012). These cover over 50% of the land area of the peninsula and islands, and will protect wildlife from some of the most extreme future land-use changes. I fear that the presence of introduced goats and other non-natives on off-shore islands will need an urgent response if the threats are to be confronted. There are encouraging initiatives such as the establishment of the NGO ‘Native Plants of the Californias’ to inform and educate the next generation.
We cannot afford to delay action, and we have therefore been expanding our plant conservation efforts on the peninsula with our partners at the National Autonomous University of Mexico (UNAM). Since January 2014, our fieldwork has accelerated with support of the Marisla Foundation: I am pleased that by working closely with local botanists at the Autonomous University of Baja California (UABC), and with advice from collaborators from San Diego Natural History Museum, Rancho Santa Ana Botanic Garden, Santa Barbara Botanic Garden and Botanical Research Institute of Texas, we have already secured 200 collections of seed from the peninsula for long term conservation at UNAM and the Millennium Seed Bank.
The islands of the Sea of Cortes: a fragile paradise
I had the chance in October to join a trip to one of the best preserved islands in the Gulf of California, Isla Espiritu Santo, and to see for myself a wonderful diversity of native plants set in the most dramatic landscapes. On landing at Bonanza beach by a local ‘panga’ boat, we climbed the dunes where Dr Jon Rebman drew our attention to a curious plant Proboscidea althaeifolia in the Martiniaceae family that produces ‘devils claw’ fruits. These have evolved to attach to the lower leg of large animals and thus disperse its seed. Visitors to the Millennium Seed Bank at Wakehurst may have seen massive models of an African ‘devils claw’ species that disperses seed in a similar manner.
Further exploration beyond the coastal mangrove thickets and amongst wind-sculpted rock formations on the sister island of Partida revealed a diversity of cacti: for example, Stenocereus gummosus which produces edible ‘pitahaya’ fruits and the majestic organ pipe cactus Stenocereus thurberi.
What more needs to be done?
Although I am alarmed that many habitats continue to be lost and fragmented on the mainland, my short visit to Isla Espiritu Santo demonstrated the importance of achieving World Heritage Site protection of these fragile environments in 2005. The efforts of the protected area managers combined with the high standards of the eco-tourism operators appear to be effective at present, but continued investment will be needed to control non-native species and to manage appropriate use of the islands in the face of increasing recreational pressure.
On the peninsula and islands, we will continue to target habitats at greatest risk of change, including vernal pools and coastal dunes, and will work alongside NGOs and University collaborators to share botanical information and achieve greatest combined impact of our work. I am pleased that our seed collecting effort will also complement the ‘California Endangered Plant Rescue programme’ which Kew is supporting in the USA through the Center for Plant Conservation.
Through these projects, we can also help mitigate the longer term threats from global climate change and invasive species, specifically by building expertise and ex situ collections that could be part of a targeted response. I am already planning my next visit to this precious region.
I’d like to thank Kew’s partners and my colleagues Dr Tiziana Ulian and Dr Wolfgang Stuppy for their important roles in this project, as well as the Marisla Foundation for providing funding.
Rebman, J. P. & Roberts, N. C. (2012). Baja California Plant Field Guide, third edition, San Diego Natural History Museum
Vanderplank, S. & Excurra, E. (2015). How marine influence controls plant phenological dynamics in Mediterranean Mexico. Journal of Plant Ecology doi: 10.1093/jpe/rtv066. Access this article online
Las Californias Binational Conservation Initiative (2015). Las Californias Binational Conservation Initiative