Flora of the Galapagos Islands
How does Plantlife come to a Volcanic Island?
All of the plantlife of the Galapagos Islands originally came from somewhere else. The islands are volcanic, which means they were formed millions of years ago when volcanos under the ocean's floor erupted repeatedly, building up walls of cooled lava. The walls formed a cone around the pressure point where hot lava exited the earth's floor, and the cone rose until it breached the surface of the ocean. Eventually, we have a string of these volcanic structures, formed in an archipelago, creating the Galapagos Islands. At first, the volcanic islands were totally devoid of life until bit by bit seeds and organisms were brought here by birds, the wind or by flotation on the seas (called rafting.
Sixty % of the seeds brought to the Galapagos Islands were brought by birds. Wind is reponsible for 31% of seeds that arrive here, and the last nine% come to the Islands via rafting. As you can see, birds play a major part in what types of plantlife take root in the Galapagos Islands.
South American Influence
99% of plantlife on the Galapagos Islands comes from South America. The rest is from Mexico and other parts of Central America. As more Ecuadorian settlers arrive on the Islands, the number of introduced species rises as well. As of 1986, there were 240 introducted species of flora on the Galapagos Islands. Some of the islands have more plants than others, and have more varieties of plant species than others, too. The determining factor here is whether the island has much elevation. Larger islands with higher hills or mountains will have more vegetation zones in which to hold a wider variety of plantlife. They'll have more soil, more varied climate, and different types of conditions at different elevations so variety of plant species will be greater. Of course surface area plays a role as well, but a slightly smaller island with more elevation will hold a greater diversity of plantlife than a slightly larger island that's totally flat. Diversity is important to all life, so plants will be more apt to thrive in conditions where there are different types of species in different conditions.
Vegetation Zones
There are seven vegeation zones in existence in the Galapagos Islands. Not all of the islands have each and every zone, however.
Seven Vegetation Zones found on the Galapagos Islands
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- The Littoral Zone
- The Arid Zone
- The Transition Zone
- The Scalesia Zone
- The Brown Zone
- The Miconia Zone
- The Pampa (Fern) Zone
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The Littoral Zone
his will be the zone that's closest to the sea, at the lowest elevation. The vegetaion in this zone is influenced by salt, mostly mangroves here. Mangroves have oval-shaped leaves and there are four types:
- Button Mangrove
- Red Mangrove
- White Mangrove
- Black Mangrove
Other plnat species found in the Littoral Zone are the saltbrush Cryptocarpus pyriformis, which has fat leaves and is found everywhere on the Galapagos Islands. The grow to be up to six feet tall. Locally, they are called monte salado. Other species in this zone are succulents called Sesuvium portulacastrum, which are bright colorful annuals with small oval-shaped leaves that are either red or green. Flowers can be pink or white.
The Arid Zone
The Arid Zone covers more area than the lower-lying Littoral Zone, and is found in elevation just above the Littoral. Cacti are the most common forms of vegetation found in the Arid Zone. To adapat to highly arid conditions, the cacti have developed very small leaves, a very strong ability to engage in photosynthesis, development of spines and very deep roots, and leaves that point themselves at all times towards the sun. The main types of cacti found in the Arid zone of the Galapagos Islands are:
- Jasminocereus
- Opuntia
- Brachycereus
The Palo Santo, or Bursera graveolens, is also prevalent in the Galapagos arid zones. The Palo Santo is a tree which has white bark and leaves that appear only during the wet, rainy season. In fact, the wet season brings all sorts of flowering annual plants to the arid zone of the Galapagos Islands.
You'll also find acacia, in small shrub sizes in the Galapagos Islands. The Acacia have tiny leaves, yellow flowers, and small brown bean-like fruit. There are also the following plants:
- Muyuyo, or Cordia lutea, which is a tree with yellow flowers, found most on Santa Cruz Island at Acaademy Bay.
- Chala, or Croton scouleri, is a shrub with orange or yellow leaves and grey stalks. The sap will stain your clothes.
- Manzanillo, or Hippomane mancinella, is a tree that can grow much taller than other vegetation in the zone. The fruit looks like apples but is very toxic to humans. Stay away!
The Transition Zone
Next up in elevation just above the Arid Zone is the Transition Zone. There are also Palo Santos here, but the dominant plant here is the pega pega, or Pisonia floribunda, a short tree with wide branches. Lichens live in the bark of the pega pega, which is how the tree got its name. Pega pega means "stick stick", and if you touch the bark, it will "stick" or grap onto your fingers because of the lichens.
The Guayabillo, or psidium galapageium, is another spread-out tree in the Transition Zone, and its bark is soft and grey colored. The fruit is like the guayaba.
The Scalesia Zone
This can also be called the Humid Zone, and lies just above the Guayabillo Zone in elevation. There is constant precipitation in the Scalesia Zone, thanks in part to the garua or wet season. Because of the high humidity, the vegetation is dominated by ferns, grasses, and mosses but especially Scalesia pedunculata. Commonly called lechoso, this is a sunflower tree which can grow to be up to thirty feet tall and grows in dense forests. Mosses hang from the branches and the flowers are like small white daisies. A scalesia forest is beautiful, and to see one you can go to the island of Santa Cruz.
The Brown Zone
Above the Humid Zone we have the Brown Zone, which can be considered to be the tapering off of the humid zone. There are till scalesia trees, but the mosses that hang off the branches of the scalesia in the Humis zone no longer thrive in the brown zone. Here, they fall off and the result is lots of brown color, hence the name of the zone. The dominant vegetation is Liverworts. Liverworts will also cling to the scalesia trees, but they do not depend on the trees for life.
The Miconia Zone
Going up, there is the Miconia Zone. Named after the dominant type of vegetation found in here, the zone is located at the 1000 meter level above sea level. Miconias are leafy bushes with oval-shaped leaves that look like the leaves of teh cacao. The flowers are pink or purple, and the species is found only on Santa Cruz Island and San Cristobal. The species is endemic.
The Pampa Zone
At the top of the chart, or at the summit of the volcanic islands of the Galapagos, we have the Pampa Zone. Needless to say, because of the high elevation, it's windy here, and it's also misty. Trees have a hard time thriving in the Pampa zone, so the main form of vegatation is ferns, sedges and grasses. The conditions are swampy, and you will find waterholes in collapsed lava tubes with mosses and ferns growing inside. These watery lava tubes are also an excellent place to find orchids. There is one type of tree found in the Pamapa Zone of the Galapagos Islands: the tree fern, or Cyathea weatherbyana, which grows to about 10 feet.
Introduced Species of Vegetation in the Galapagos Islands
The Galapagos Islands have had 240 species of plants brought in by human intervention. Farmers and settlers brought with them plants which have, in some areas, taken over the native species of plants. This happens especially on San cristobal, Floreana, and Santa Cruz. The introduced species have upset the balance of ecology in many areas, and the Galapagos National Park Service has been particularly concerned about this.
20 percent of the 240 introduced species come from North America and Europe, and some of them are very agressive in dominating their surroundings. In other words, they are very good at dispersal, and quickly invade and destroy native plants.
Herbicides have been used against guayaba, one of the most insidious introduced species in the Galapagos Islands.
Introduced Species in the Galapagos Islands
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- Elephant Grass
- Cabuya Cactus, or Furcraea cubensis
- Pinnata, or Kalanchoe
- Guayaba, or Psidium guayaba
- Lantana, or Lantana camara
- Pomarosa fruit, or Eujenia jambos
- Pangola, or Digitaria decumbens
- Aguacate avocado, or Persa americana
- Toronja Limon fruit, or Citrus spp
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