Plants are the basis of all life within the Galapagos Islands.
Of the 500 species of "higher" plants 40% are endemic.
These plants combined with the 200 species of introduced plants and 500 species of mosses, lichens and liverworts give the Galapagos its complex ecosystem.
The island's flora lives in specific zones.
Understanding these zones helps with identification and appreciation of the flora.
From the Mangrove Swamps that cover the wet coastal zone and the Prickly Pear Cactus of the Arid Lowlands to the Scalesia Trees and Miconia of the higher Humid Zones the Galapagos hosts an interesting array of flora.
- Life Zones
Climate on the islands varies from dry low areas along the coast to the high moist areas near the volcano tops. In total there are 7 zones within the archipelago
Various plants and animals have adapted over the years to the conditions of the islands and in some cases the condition of the zone. Flora is normally found in a specific zone, and the fauna dependent on those plants can be found there as well. Some birds and animals migrate between zones depending on conditions.
- Coastal Zone
The lowest life zone on the island is the coastal zone. Those plants that exist on the seas edge can be divided into two portions the Wet Coastal Zone or Mangrove Zone and the Dry Coastal Zone or Beaches and High Tide Areas.
Mangroves live in the Wet Coastal Zone. These salt-tolerant trees and shrubs thrive in shallow and muddy saltwater or brackish waters. In the Galapagos there are 4 varieties of Mangroves including the Black Mangrove, White Mangrove, Red Mangrove , and Button Mangrove.
The Dry Coastal Zone is made up of the dry sandy area from the sea to the high water line. This area supports low lying spreading plants which are able to retain water including the Sesuvian Portulacastrum an herb whose stem turns a bright reddish color during the dry season.
Arid Lowlands Zone
As an island slopes from the beach to an elevation of about 197 ft (60 m)
elevation an arid desert like zone occurs. This region is home to the many Cactus that live in the Galapagos including the Prickly Pear Cactus, Lava Cactus and Candelabra Cactus . Vine plants also make their home in the Arid Lowlands. The endemic lava morning glory and endemic passionflower can be found in this zone.
At the top of the Arid Lowlands the silvery leafed Palo Santo Tree with its collection of lichens can be seen.
Rising up the island plants become more frequent. In the Transition Zone plants from both the Arid Lowlands and the Upper Moist Zones occur. This zone is home to a variety of small trees or shrubs including the endemic Pega Pega Tree and the endemic Guaybillo, which produces a small white flower that develops into a fruit similar to its cousin the Guava.
The Galapagos Tomato, endemic to the islands is a salt resistant tomato that has been used to create a hybrid, which is capable of growing in salty soil around the world.
- Scalesia Zone
The lowest of the "humid" zones this zone is named for the daisy tree that grows between 970-1970 ft (300 - 600 m) elevations. The Scalesia is one of the few trees in the Aster Family and grows to heights 16 - 50 ft (5-15 m) in height. Its trunk and branches are covered with moss and lichens. This area is humid and has the essence of being in a rainforest.
Scalesia Trees have been greatly reduced in numbers since humans arrived in the islands. With them came pigs and goats, which devour the young plants and feed on older plants. People also introduced the Guava, a plant whose dense growth patterns steals nutrients and eventually makes it impossible for competing plants to survive.
- Miconia Zone
Above the Scalesia Zone at 1950 - 2300 ft (600-700 m) is the humid zone named for the Miconia shrub that once dominated this region. The Miconia Robinsoniana grows to heights of 10-13 ft (3-4 m). It's leaves easily identify it with their yellow or reddish shading on the edges.
The Miconia is endemic to the Galapagos, but since the arrival of man it has become the most endangered plant in the islands. Introduced cattle have grazed the Miconia into dangerously low levels.
- Pampa Zone
On islands with elevations over 3000 ft (900 m) the highest vegetation zone in the Galapagos can occur, the Fern-Sedge Zone or Pampa Zone. The appearance of this zone depends on the amount of moisture it receives. This region contains no true trees or shrubs. The tall Galapagos Tree Fern and Liverworts are commonly found in this zone.
Mangrove Swamps consist of a variety of salt-tolerant trees and shrubs that thrive in shallow and muddy saltwater or brackish waters. Mangroves can easily be identified by their root system. These roots have been specially adapted to their conditions by extending above the water. Vertical branches, pheumatophores, act as aerating organs filtering the salt out and allowing the leaves to receive fresh water.
Mangroves are thought to have originated in the Far East then over millions of years the plants and seeds floated west across the ocean to the Galapagos Islands. Mangroves live within specific zones in their ecosystem. Depending on the species they occur along the shoreline, in sheltered bays, and others are found further inland in estuaries. Mangroves also vary in height depending on species and environment. The Galapagos is home to 4 types of Mangroves:
- Black Mangrove
Black Mangrove ( Avicennia germinans) has the highest salt tolerant leaves of all the mangroves the leaves and is equipped with special salt-extracting glands. Trees grow to 65 ft (20 m) in height; the long spreading branches are covered by a dark brown bark. Leaves grow in pairs, leathery in texture with a narrow oval shape. The top leaf is dark green and the bottom is pale with hairs often coated with salt. The trees' yellow flowers grow in clusters developing into a green lima bean shaped fruit. Black mangroves have a carpet of short aerial roots or pneumatophores surrounding the base of the tree.
- Red Mangrove
Red Mangrove ( Rhizophora mangle) is the most common in the Galapagos named for its reddish wood. This species is used around the world as a source of charcoal and tannins for leather working. Trees grow to 72 ft (22 m) in height, yet red mangroves also can be seen as small bushes. The thick leathery leaves grow in pairs with a dark green leaf above and pale yellow leaf below. Red mangroves have yellow flowers that grow in groups of 2 or 3. Red mangroves can be seen growing near the low tide zone as well as at higher elevations mixed with other mangrove species.
- Button Mangrove or Buttonwood
Button Mangrove or Buttonwood ( Conocarpus erecta) is not a true mangrove, yet this tree usually found in the higher mangrove elevations. They have dark gray bark and leaves which are either oval, leathery and smooth green or sharply pointed with salt glands at the base. Buttons have green flowers that mature into a round purple fruit.
- White Mangrove
White Mangrove ( Laguncularia racemosa) grows into a shrub with aerial roots close to the water. They thrive in areas with infrequent tidal flooding. Leaves are smooth, oblong and light green in color with notched tips.
- The Importance of Mangroves to the Ecosystem
Mangroves are a unique part of the coastal ecosystem. The fallen leaves and branches from the mangroves provide nutrients that support a variety of sea life. The shallow waters within the Mangrove swamp provide a nursery for young fish, crabs, shrimps, mollusks and rays. Mangroves provide a nesting area for hundreds of bird species. In the Galapagos Mangrove Finch, Medium Ground Finch, Dark-Billed Cocos, Herons, Yellow Warblers, Mockingbirds and Small Ground Finch all can be found in the Mangroves.
Mangroves help protect the coastline from erosion, storm damage and wave action. They prevent shoreline erosion by acting as buffers, catching the soils and other materials that run off the land and stabilizing the soils and nutrients lost from erosion.
- Galapagos Cactus
In the dry inland portions of the Galapagos Islands the most common plant is the Cactus. These succulents, able to store water in their stems and leaves, thrive in hostile climates and during times of drought. Most cacti have spines, which have evolved from leaves. The spines are a fundamental part of the Cacti, used to guard against grazing animals making the plant difficult to chew, offer shade keeping the internal temperature of the plant down, and it channels any rainwater towards the base of the plant. The waxy coating that covers the skin of the cactus known as the glaucus bloom reduces evaporation by the plant by holding in moisture. Leaf like stems known as pads store and conserve moisture and works as photosynthetic organs for the cacti.
Endemic cacti in the Galapagos include the Lava Cactus , Candelabra Cactus , and the species of Opunt ia (Prickly Pear) found in the Galapagos.
Prickly Pear Cactus ( Opuntia Cactaceae)
Prickly Pear Cactus is the common name for plants of the cactus family. Native to the tropical and
subtropical regions of the United States, Baja California and the Sonora Desert region of Mexico these plants have spread out throughout the world's tropical regions.
An endemic cacti it is also the most common cacti in the islands. With its yellow flowers it grows like a shrub, except on islands where herbivores are a threat then trunks can grow to 5 ft tall. The Prickly Pear Cactus is the staple of the Land Iguanas & Tortoises' diet. Their flat jointed stems covered with small stiff hairs and spines identify the cacti. The yellow flowers develop into an orange-red thorn covered fruit.
Prickly Pear have developed into 14 separate types ranging from the Opuntia Echios variation Gigantea which grows to 40 ft. (12 m) in height to the Opuntia Echios variation Barringtonensis found on Santa Cruz whose truck measures 4 ft. (1.25 m) in diameter. These Galapagos Cacti provide the habitat and food source for many of the birds and animals on the islands including 2 species of Finch, Iguanas, Doves, Tortoises and Mockingbirds.
- Lava Cactus ( Brachycereus Nesioticus)
Growing in lava fields as their name suggests, these small cactus grow in clumps measuring up to 23 in (60 cm) in height. New growth on the cacti is yellow as the cacti mature the color fades becoming paler and eventually becomes a gray or black color with age. T he creamy white flowers are visible in the early morning hours only, and have normally faded by 8 in the morning.
- Candelabra Cactus ( Jasminocereus Thouarsii)
Named for its shape this large endemic cactus grows to heights of 23 ft (7m). Its tube shaped pads resembles the Organ Pipe Cactus of the Sonora Desert. The green or red flowers are 1 - 2 inches (2-6 cm), which open before dawn, develop into fruit of the same colors. The Candelabra Cactus can be seen on the cliffs outside Puerto Ayora on Santa Cruz.