• John Mendelsohn

Natural Fire Breaks?

Fires could do great damage if they could get into the fairy forests shown in the previous blog, which leads us to the intriguing possibility that miombo trees manage to keep fires away by forming fire breaks on the forest edges. This is exactly what often happens when the fires reach the pale white fringes visible in the image, and then die off. Little grass or shrubbery grows in these pale areas, and so there is little to burn. In effect, the bare forest margins are good fire breaks.

The question is, however, what prevents grass and other plant growth around the miombo forests. One plausible hypothesis is that forest trees produce chemicals that are specifically poisonous to grasses and other plants that burn easily. These are called allelopathic chemicals, which many other plants produce to protect themselves against competitors and foraging mammals. Thus, allelopathic chemicals produced by miombo tree communities may leach or diffuse out of the forests to poison the surrounding margins, which are generally between 10 and 50 metres wide in this area of eastern Angola.

An energetic young scientist needs to test this suggestion. If support for the hypothesis is found, a next step would be to identify the compounds and to think of other useful ways in which these chemicals could be used. Much that is good - and useful - is yet to be found in Africa’s forests!