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Sarah Sinn-White, expedition guide, Safari Endeavour, March 2016

As the Safari Endeavour cruises from island to island through the Gulf of California, I think about how differently my seasons in Alaska compare to my season down south.

As a plant enthusiast, my first thoughts go to the different species we are observing. Obviously we have moved from the green, damp temperate rainforests of Southeast Alaska to the southern, dry Sonoran Desert. But it’s not just the different species distribution that is so striking; it’s the shapes of the plants themselves.

Cactus field in the Sonoran Desert

Cacti dominate this landscape. From forty foot cardon cacti to minute hedgehog cacti, everything about this landscape requires planning and adaptation. Cacti are a special family as they have evolved to no longer require leaves for photosynthesis. This is a task that they are able to accomplish straight through their epidermal walls. The spines that we have become intimately familiar with are simply modified leaves that were lost through the evolutionary process of desert adaptions.

Flower blooming on cactus

The flowers sprout from the crown and open only for an extremely short period of time, a single night in some species. Giant barrel cacti bloom with a tricky false-nectary spine at the base to lure away nectar stealing ants from the main flower blooms. Moths and bats dominate this pollination landscape, accomplishing in a night what butterflies and bees require days to do. A species of sphinx moths found here in Baja can fly over 34 miles per hour, pollinating cardons that are fleetingly available.

Cactus in Mexico

But it’s the ribs and pleats that are the most eye-catching of all the cactus desert adaptations. Pleats serve many purposes for cacti that include keeping away herbivores as well as lessening water consumption and loss. The troughs between pleats create micro habitats for the surface of the cactus, creating an almost 70 percent shaded habitat at times.

Cactus spine with flower

The pleats also slow down the drying desert wind as it pulls away moisture during transpiration. Ribs separating the pleats serve the most essential function for cacti during water conservation. As water is seldom available for uptake, when it does occur, it’s necessary to maximize the amount of water that the plant can hold. Ribs, rather than a solid woody center, allow for vast expansion during water uptake periods. During heavy storms one can actually watch the pleats expand with water like an accordion.

Guests with tall cactus in Mexico

As much as I love the temperate rainforests of the Pacific Northwest and Southeast Alaska, I have become a desert rat during my time in Baja. Towering cardons and fat barrel cacti will always have a soft spot in my heart. Alaska calls me back, but I dream of Baja California.



Desert Adaptations

05-03-2016

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