GALAPAGOS TREES

When you arrive in the Galapagos you'd think that the islands were quite inhospitable to trees. For the most part, you'd be right. The arid lowlands receive too little rain to sustain expansive forests we might expect in the tropics. A few species are adapted to survive, but mostly only a few species of cacti and specialist plants do well.

Trees find a more welcoming environment higher up as temperatures cool slightly but, more importantly, rainfall is higher. Vegetation in the Galapagos is strongly stratified according to the availability of moisture and trees obey the dictates of the climate. (For more information see vegetation zones.) Coastal trees are predominantly mangroves; no others can survive tides or the salt laden winds. In the dry zone common trees include palo verde (Parkinsonia aculeata), poison apple (Hippomane mancinella), muyoyo (Cordia lutea) and four species of acacia (Acacia spp.). Transition zone trees are primarily Galapagos guava (Psidium galapageium) and two species of palo santo (Bursera spp.) while introduced bamboo (Bambusa gradua) is spreading into native forests. The scalesia zone is dominated by daisy tree (Scalesia spp.) of which about 14 species are known. Tree fern (Cythea weatherbyana) and cat's claw (Zanthoxylum fagara) are also present on several islands.

These and other native vegetation are threatened by cattle grazing and invasive introduced species such as guava (Psidium sp.) and quinine (Cinchona succiruba)—a problem that is proving increasingly difficult to overcome.