Forest fires which have engulfed Bogota in smoke over the past week have been fueled by highly flammable foreign plant species that have invaded Colombia's capital, experts say.
Eucalyptus, pine and gorse cover the Andean mountain range bordering the east of Bogota, where four wildfires have broken out in the past week.
These trees and shrubs contain oils and saps that are very flammable, and "help maintain the fire for hours and even days," said biologist Arnold Garcia Samaca, of the National University of Colombia.
Additionally, fire helps them reproduce and "they take over larger areas, displacing native vegetation."
Amid hot, dry conditions linked to the weather phenomenon El Nino, fires have devastated more than 17,000 hectares (42,000 acres) across Colombia over the past three months, the authorities say.
Eucalyptus trees, almost all of which are native to Australia, and the European pine, were introduced in Bogota at the start of the 20th century, as urban growth fueled demand for wood.
The common gorse shrub, native to much of western Europe, was planted in the 50s in a bid to halt soil erosion. The Bogota's mayor's office said it has since been declared one of the "100 most aggressive and invasive species in the world" and is "a threat to biodiversity."
Bogota authorities have removed more than 130 hectares of gorse in the past four years -- no easy task in the hard-to-access areas in which it grows.
Jose A. Munoz, who works with the Landscape Ecology and Ecosystem Modeling Laboratory (Ecolmod), said the underlying problem was authorities seeking the "fastest route" to control deforestation and other issues.
"Planting for the sake of planting is never going to be the solution," he said.
The environmental authority which manages the mountain range, the Regional Autonomous Corporation (CAR) of Cundinamarca, told AFP it would put in place a reforestation plan using local species such as cedar, encenillo, and white rosemary.
On Saturday, Bogota closed some 40 parks and hiking trails due to heavy smoke from the wildfires.
Authorities have recommended that residents remain inside as much as possible and wear masks if they must go out.
