Darwin’s Unrequited Isle (part 2)

During our field trip to Tenerife the two vehicles covered over 900km each, which is not bad on an island only about 80 km in length along its main axis.  We experienced temperatures that ranged in one day from a few degrees above freezing to the mid 20s centigrade.  Up in the laurel forest I mentioned last week the weather was cold and foggy, whilst in the Malpais de Güímar it was hot and dry and we sunburned.  We put in long, tiring days of walking transects, identifying, measuring and recording plants, and observing bee and bird behaviour.  And there were ticks that had to be picked off skin in one of the barrancos we visited.  The Romantic Adventurer within me would therefore like to believe that the aching limbs and upset stomach I suffered when we got back to the UK were due to some exotic virus passed on by these blood sucking arachnids.  However the Cynical Traveller thinks it was more likely to be due to a hamburger of dubious age and temperature that I ate at Tenerife Sur airport on the way home.

The Tenerife Field course was hard work but great fun and I think (I hope!) the students learned a lot.  At the very least they have now experienced just how diverse habitats can be on a small oceanic island.  In that diversity rests both the beauty of Tenerife and part of its scientific interest.  This variability in habitats is a result of its altitude (Tenerife is the second highest oceanic island in the world after Hawaii), subtropical latitude, climate, proximity to Africa, and geological history.  In a single day one can travel from high alpine habitats, through sub-alpine desert scrub and pine forest, into succulent dominated low altitude desert scrub, back up to laurel forest (a form of subtropical rainforest), as well as distinct deep valley and strandline vegetation.

Add to this the occasional hurricanes and forest fires that tear across parts of the island, not to mention volcanic eruptions, plus the human impact, and it makes for a rather dynamic environment at a range of time scales.  These processes probably add to the overall biodiversity, as predicted by the intermediate disturbance hypothesis, plus formation of new land area can select for novel proto-species.  It begs the question of whether volcanic oceanic islands are more diverse than their coralline counterparts, which we might expect to be less dynamic environments.  Has anyone investigated this?  That’s one of the things that keeps my interest in biodiversity going: there are too many questions for a single lifetime.

I’m hoping that “Darwin’s Unrequited Isle” will take off as a new name to refer to Tenerife, replacing the Island of Eternal Spring cliché it currently holds (and shares with Madeira).  Especially as many of the days we were there were spring-like only in the sense that they were wholly unpredictable.   On the roof of Tenerife, in Las Canadas, our car thermometer registered 3 degrees centigrade at 1100am.  And it snowed.  I’ve never experienced that at this time of the year.  We’ve had torrential rains storms but never snow.  In late April.  In the “Island of Eternal Spring”.   I’m not complaining though, it all adds to the fascination of this most interesting of islands and is why we come back year after year.  It’s also better conditions than my colleagues Duncan McCollin and Janet Jackson endured with those students who elected to do field work in Northamptonshire rather than Tenerife.  For most of the time we were away it poured with rain back home, turning the drought-imposed hosepipe bans into flood warnings in some places.

Needless to say, the day of the snow was the day we were due to make some observations of bee behaviour.  By and large bees don’t like snow and low temperatures ground most of them.  So that planned activity was delayed until later in the day when it finally warmed up sufficiently for them to start flying.

This theme of variability in the weather, on a day-to-day basis and compared to previous years, was a recurring one all week.  Tuesday was hot, as I recounted in my previous blog.  But Wednesday was a huge contrast as we headed up into the cold, wet laurel forests of the Anagas Mountains.  It’s always a little chilly on this part of the island due to the prevailing moisture-laden trade winds, but this year was colder and foggier than I can remember.  The students collected data on the distribution of plants up a vertical cliff face that we can compare to similar data from another site collected last year.  I’m intrigued by the way succulent plant groups such as Aeonium and Monanthes are able to survive on these water limited, nutrient poor environments, vertical versions of the desert scrub lower down the mountains.  These succulents add to local plant species richness within the forest and provide nectar and pollen resources when they flower, increasing the overall levels of biodiversity of an already diverse habitat.

As well as studying plant diversity we also did some work with the animals of Tenerife.  The bees I’ve already mentioned, but for the first time we also made some observations of how bird behaviour changes in tourist areas compared to more isolated spots.  Even within a very short distance, no more than a few hundred metres, it’s clear that bird diversity, abundance and range of observed behaviours were greater in the areas where tourists congregate to barbecue and relax.  We did some similar work with lizards for a few years and found that they were bolder close to tourist car stops than further away.  Humans can impact the life of this island in very subtle ways.

We also spent a morning with volunteers from the Atlantic Whale Foundation (AWF) on one of their trips out to record individual whale and dolphin activity off the south west coast.  The AWF piggy backs on one of the commercial whale watching boats and the students are encouraged to think about the synergies and tensions between the conservation-motivated scientific observation of the AWF and the commercial motivations of the tourist boats.  It gets to the heart of what “eco-tourism” is all about and the point at which it does more harm than good.  The only strong opinion that I have about it is that the value of eco-tourism is context dependent; some activities are better than others in some circumstances but not others.  Regardless, the trip is always popular with the students (except one year when a student spent the whole time aboard with her eyes closed, suffering chronic sea sickness) and this year was exceptional, with great views of bottle nosed dolphins and pilot whales, as well as long distance spottings of common dolphins and a 20m fin whale.

The final day of the trip, prior to getting to the airport, is traditionally spent at the Pyramids of Güímar ethnographic park where the students discover some of Thor Heyerdahl’s left field views about possible pre-Columbian links between Canarian, Mediterranean and New World peoples.  Whatever the truth behind the origin and function of these enigmatic structures, the visit is a pleasant way to end the field course.  Nestled within the protective bowl of the Güímar Valley, I often wonder if it’s a coincidence that the Güímar structures look out towards the three cinder cones adjacent to the Güímar Badlands.  Approaching from the south along the TF1 road, these hills take the form of a heavily pregnant woman lying on her back.  Was it of symbolic significance to the ancient Tenerifeans in the days prior to the Spanish conquest?  I like to think so though we probably will never know.

A small grant from the British Ecological Society means that I’ll be back in Tenerife at the end of May for ten days to do some follow up field work.  Hamburgers will be avoided.

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