Plants and rocks: a special bond
You might know the Galápagos are volcanic islands. But how exactly did they form and why did life come to flourish here? To better understand this, we need to look at plate tectonics and ‘hot spots’. There are seven major tectonic plates that make up the ‘jigsaw puzzle’ of the Earth’s crust and upper mantle, with the Galápagos lying right on top of the Nazca Plate. This plate is moving toward the South American continent at a rate of 2.7 inches a year, carrying the islands along with it.
Underneath certain plates, intense heat from within the Earth is transferred to the surface. Here, magma bubbles up through cracks and crevices, solidifying until it eventually breaches the surface of the ocean. This can sometimes be accompanied by truly violent eruptions, lifting up whole sections of the seabed and blasting rocks and lava into the sky. Volcanic islands then appear in the middle of the ocean, creating familiar landmasses such as Hawaii, the Azores and, of course, the Galápagos.
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But these processes can take millions of years, and as the plates keep moving the hot spot remains anchored in the same place, creating new volcanic islands. This forms chains of islands similar to how a confectioner squeezes out dollops of icing through a nozzle. In the Galápagos, the islands to the east are far older than the western ones. This implies that the hot spot is currently below the islands of Isabela and Fernandina, the westernmost outcrops, while the islands in the east are eroding and sinking back into the ocean.
On your visit, notice the stark differences in landscapes, especially if you travel from east to west. In effect, you’re traveling forward through time, from the distant past to the more recent past. The islands in the east are visibly older, more eroded and more arid than the younger ones in the west, which are more verdant and hillier. There are 13 volcanoes still active on the western isles. If future eruptions occur, it would be here.
When the plants arrived
Much like the animal species that first arrived here, the first plant species to colonize the Galápagos had to be hardy pioneers. It’s likely that spores and seeds were carried on the wind or tides and ended up landing on the barren shores of the newly formed islands. Others could have arrived in the guano of migratory birds. The only way for them to germinate and grow would be to fuse with the rocks and survive on a bare minimum of water and nutrients.
To make the challenge even greater, with no pollinating insects, plants would have had to reproduce in novel ways. Nevertheless, a few hardy species did manage to put down roots (pun intended!), thus starting the process of building up topsoil and making it possible for other life forms to survive. Today, many of the trees growing on the islands can trace their lineage back to humble ‘weeds’ such as daisies and dandelions—the true masters of colonization. Without these initial plants, the islands would have remained barren volcanic wastelands, with little to no terrestrial life.
Know your vegetation zones
Distinct vegetation zones have formed on the islands, given their differing ages and other factors including altitude, oceanic currents, and rainfall patterns. In general, life becomes richer and lusher as we progress westward through the chain. Altitude also makes a big difference. For example, the highlands of Santa Cruz are green and moist enough to support a relatively large population of giant tortoises, while the spiny and brittle landscape of Española support much less terrestrial life.
The state of the island vegetation and life in the surrounding seas varies depending on the El Niño and La Niña cycles. In El Niño years, ocean productivity fares poorly and marine life has a difficult time. Nonetheless, the increased rainfall means vegetation and land animals thrive. The opposite is the case during La Niña years, when the dry weather disrupts land-based life, but oceanic life thrives.
Areas close to the tidal zone on islands are ideal for plants that tolerate saltwater, such as the red mangrove, with its distinctive aerial roots. Mangroves are important for fish species as nurseries, but due to the limited availability of nutrients in the shallow waters, these semi-aquatic trees grow very slowly. Interestingly, the roots of red mangroves are raised up in the air, where they absorb oxygen more easily than submergedunderwater.
This is mostly cactus territory, but other plants can (and do) survive here, including various shrubs. There are several different types of cacti, but theopuntia(otherwise known as theprickly pear) is the easiest to spot.Its succulent pads have a high moisture content and on some islands, it is the main source of food and water for reptiles. Birds help disperse its seeds, which are contained in the fruit.
On some islands, we find a humid zone, where epiphytes such as orchids, mosses, ferns, and lichens thrive, due to the constant moisture and heat.In this zone, it is typical to find trees and shrubs with colorful flowers and foliage. The high degree of humidity supportsscalesias, a type of tree that’s actually a descendent of the humble daisy. Scalesias form dense forests filled with numerous species of birds and reptiles.