México
Baja California
Interestingly, mangrove dynamics are only climate-driven in North America, as they are protected under Federal law in the United States and Mexico alike. This allows for interesting comparisons between populations at the physiological level. Although there has been an extensive amount of research conducted on the Atlantic Coast, the Pacific coast mangroves are presenting us with important biogeographical questions.
My research focuses on the mangroves’ northernmost range limit on the North Pacific coast, which currently occurs in the southern part of Baja California, Mexico. Mangroves forests in Baja California support a diverse array of associated species and provide considerable ecosystem services to human communities, yet we still know relatively little about how climate change will alter their dynamics. Unlike the Atlantic coast of North America, where mangroves range limit is controlled by the occurrence of freezing temperatures (Cavanaugh et al. 2014), air temperatures from Baja to Southern California appear to be favorable for mangroves, however their range limit is found relatively far south in Baja, more than 3 degrees of latitude further south than the corresponding poleward range limit in Florida. To this day, the climatic and environmental factors that set the current northward range limit of mangroves in Baja are unclear, and this leads to overarching questions:
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What are the processes that control the current mangrove distribution along the Pacific coast?
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Has their habitat shifted in response to past climate change?
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Will they be able to migrate poleward similarly to what has been observed in Florida?
I had the opportunity to work with plant physiologists during my Graduate Student Fellowship at the Smithsonian Environmental Research Center under the supervision of Dr. John Parker. I spent six months growing seedlings from different mangrove populations and analyzing their physiological traits, in order to compare their fundamental physiological niche to current conditions (their realized niche).
This comparison led to significant differences between the Pacific and Atlantic coasts, and provides us with insights on each mangrove population’s potential response to climate change. These physiological experiments at the individual level enabled me to tease out different environmental stressors, and I was able to determine significant relationships between thermal tolerance to air and water temperature, and aridity.
This is providing us with insights on each mangrove population’s potential response to climate change, as we determined that on the Atlantic coast, range limits for both mangrove species are set by extreme cold air temperatures and rapidly shifting in response to climate change. On the other hand, n the warmer but more arid Pacific coast, range limits for black mangroves only appear limited by cold air temperatures, but neither species seems to be undergoing climate change-related migration. This could be due other range-restricting factors, such as aridity or dispersal limitation.
Such findings have implications beyond the mangrove world, as they demonstrate that a series of environmental stressors (cold temperatures associated with aridity), are making these tropical trees poleward migration more uneven than previously expected.
Our study has been published in the Journal of Biogeography.
Baja California is a fascinating place to conduct field work. Being able to drive up and down the Peninsula from Los Angeles has provided us with great opportunities to explore it, and to collaborate with local scientists.
Below is a selection of field campaigns conducted over the years.
