Watching as our wild spaces burn

Watching as our wild spaces burn

03 March 2016

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Trinidad and Tobago– As dry season gets underway, we have all noticed the first bush fires of the year. Our neighbourhoods become engulfed in smoke, and some people worry for their properties, but what are the ecological consequences of bush fires? How worried should we be for our wildlife and natural ecosystems? Are bush fires ‘natural’? In recent years ecologists have come to appreciate the important role that fire plays in maintaining the vitality of certain ecosystems.

Over the history of the biosphere, fires have been a rare event for most habitats, although the frequency of bush fires is thought to have increased as early humans expanded into new areas. However, these infrequent ‘natural’ fires are now competing with the majority of bush fires that are started by modern humans with modern motives; humans are the leading cause of bush fires worldwide.

Historically, fires do not occur in ecosystems that are either too dry for lush vegetation to provide sufficient fuel, or too wet for fire to take hold. Thus, fire activity is highest in tropical grasslands and savannas, and lowest in arid deserts and moist forests.

Trinidad falls within an ecoregion where fire is not considered to be a significant part of ecosystem development, although fire may have played a role in the evolution of small areas of natural savanna (eg in the Aripo Savannas). Of the different forest stands in Trinidad, exotic pine and teak plantations are most at risk of bush fires, but any forest with an open canopy or near areas of grass or bamboo is vulnerable.

Even in normally humid forest stands, a week of consecutive dry days provides enough fuel at ground level to allow bush fires to take hold. Therefore the risk is greatly increased when the dry season is severe, as it is predicted to be this year.

Major threat Bush fires are a major threat to Trinidad’s forests, as they are largely composed of fire-sensitive plant and animal species.

As fires become more frequent, fire-sensitive species are replaced by fire-tolerant species over time, thus making the landscape more uniform and less diverse.

Recurrent fires deplete the supply of seedlings from long-lived species, resulting in more open, fire-prone forest stands.

In the most extreme case, forest cover is replaced by fire-climax grassland. Such grasslands burn frequently, preventing the return of trees and providing fuel for future fires that may spread to adjacent habitats; several examples of this can be seen on the south-facing slopes of the Northern Range.

As for much of the tropics, all of Trinidad’s natural habitats are classified as “fire degraded” due to the alteration of the natural fire regime. This disruption of the natural fire regime largely developed in the 1990s, with former plantations and State-owned forest giving way to unplanned, unpoliced, and often illegal, settlements. By the end of the 1990s, the Forestry Division estimated that each year more than 6,000 acres of forest burn and some 100 acres are permanently lost. Once the tree cover is lost, the bare soil loses its ability to retain water and may become vulnerable to landslides

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