10 June 2015

The Enchanted Isles: a Geological and Evolutionary History

A final series of Ecuador posts (by now very, very belated). The theme? Tourism and sustainability in a fragile island ecosystem. The place? The Galápagos Archipelago.

Well-known for one very specific, very clever fellow who visited in 1835 and observed some birds (as well as loads of other plant & animal species), and made some astute observations about evolution and speciation, the Galápagos are often thought of quite simply as Darwin's natural laboratory.

But they are so much more than that. They are not just a "natural laboratory" populated by dramatically (and elegantly!) speciated animals and plants; they are home to a human population as well, with centuries of human history that have been linked with the introduction of plants for agriculture and invasive species for food and as pets; and they are the annual destination for more than 200,000 tourists, bringing with them pressures for demands that far exceed the resources available on the islands - not to mention far more invasive species, on a totally unprecedented scale.

We landed bumpily on this inauspicious assemblage of rocky volcanic islands, 1000 km (620 mi) to the west of the Ecuador coastline in the Pacific Ocean, and spent 10 days taking classes, exploring the beautiful shores and venturing up into the inland ecosystems of this archipelago. We viewed it through the lens of applied ecologists: how can one possibly begin to reconcile conservation aims with the rights of inhabitants, when it is international rather than local interests driving the conservation movement there? And how can this be balanced against the increasing pressures exerted by tourism?

We'll explore the issue in three parts: background of the islands, human presence and invasive species, and tourism.

I. Geological and Evolutionary History of the Galápagos

To appreciate the importance of the Galápagos Archipelago on the conservation and tourism scene, it is important to delve quickly into its geological and evolutionary history. The islands are formed by a volcanic hotspot situated under the Nazca tectonic plate, which moves eastward a few centimeters per year. Magma emerging from the hotspot creates the islands, which are carried eastward towards the South American mainland with the movement of the Nazca plate.

The newest islands are volcanically active, and sit directly above the hotspot; as the islands are carried away from the hotspot, their volcanoes become inactive, and erosion carves away at them until the islands disappear into the ocean. So the Galápagos islands are created through vulcanism and destroyed through erosion, and this process has been going on for the past 60+ million years.

Scientists estimate that species began to arrive on the islands (which, allow me to reiterate, are about 1000 km - 620 mi from the the nearest coastline) as early as 20 million years ago. Birds arrived by flying, either deliberately or by being caught in unexpected storms. Plants arrived as seeds that floated or were borne by wind; some may have been caught on the foot/feather/beak of a bird, or were deposited in their guano. Reptiles, amphibians and mammals likely arrived floating on "rafts" of plant material. Insects were either wind-borne or arrived via the feathers and fur of other animals.

After the difficult first step of just arriving to these distant islands, species had to establish - that is, they had to be able to find enough water and food on the inhospitable archipelago (which has very limited freshwater resources). Otherwise they would die out immediately. Species that were able to adapt to extreme condition, therefore, were selected for. And species that were able to spread out and move to the different islands were also more successful, because - remember - the older islands were disappearing into the sea.

And this is the most exciting part of the geological and evolutionary tale of the Galápagos: although some of its native species have been present on the Archipelago for as long as 20 million years, the oldest of the current islands have only existed for 3.5 million years. In other words, the original islands that the first species arrived on have long since eroded and disappeared, likely taking some species with them. The species that survive now were the ones that radiated outwards amongst the islands and adapted to the new conditions on each islands. Speciation, or the process of developing specialized traits (such as the different beaks of Darwin's famous finches), was avidly selected for in the Galápagos.

For that reason, the Galápagos are something of a gem from a scientific perspective: here is this impossible world, populated by species that crossed a vast expanse of water and then underwent multiple speciation events in an extreme environment characterized by harsh conditions and limited resources. The ecosystems of the Galápagos, therefore, are incredibly special. And from a scientific and conservation perspective, they must be protected for this reason.

But what have been the challenges to that goal? Coming in the next instalments...

II. Human Arrival and Introduction of Invasive Species

III. Tourism and the Demand for more More MORE

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