Burning trees? Give me a break…


One of the big problems with plants is that their phenomenal photosynthetic efforts produce masses of dry matter. What, that’s a problem..? [Ed. – please, read on…] On the plus side, that fuels global food webs and thereby facilitates much of what happens on this planet of ours. On the minus side, when it is really dry matter, it burns incredibly well. Not only that, but essential to continuation of the combustion process itself is that gaseous waste product of the same photosynthetic process, oxygen.*

Whilst burning of plant material can be a life-giving phenomenon for those plants whose seed release and germination may be linked to the heat generated and smoke-derived chemicals that accompany that conflagration, such a ‘wildfire’ is generally a bad thing. Especially when forest fires for example get out of hand and fatalities may occur and people’s property is engulfed and subsequently consumed by the flames (e.g. the 2015 series of California (USA)’s wildfires – and the 2015 Sampson Flat bushfires in Australia).

However, and fortuitously, when it comes to combustibility – and therefore the capacity to help propagate a fire once initiated in a vegetation stand – all plants are not equal. Interest in the capacity of certain tree species to prevent fire spread has been sparked by field observations in Turkey and Spain that common cypress trees (Cupressus sempervirens) are sometimes less affected than other tree species by wildfires. Could such trees be planted and used as a natural fire-break, i.e. help to stop fire spreading beyond them to the next available pile of combustible plant material?

Investigating this possibility in laboratory-based studies, Gianni Della Rocca et al. conclude that C. sempervirens var. horizontalis is relatively resistant to ignition because of such factors as its high ash content and the ability of the leaves to maintain a high water content during the summer. The latter quality is presumably related to the cypress’ ability to tolerate prolonged drought, which is doubly important/relevant because conditions which lead to drought – e.g. low rainfall/high temperatures – often lead to drying-out of plant material which enhances its flammability.**

At the risk of making a bad – and phytotaxonomically incorrect! – pun, is this an example of fighting fire with fir..? As always with small-scale, laboratory-based studies there is need to see if this also works in the ‘real world’, natural situation . Testing this would presumably require stands of suitably mixed forest and people to deliberately set them alight. I don’t know where you’d get such individuals from, maybe you’d need to advertise for participants. So, can you imagine the advert, which may start thus, “Arsonists wanted: Previous experience not essential…” ***

* Plants, architects of their own downfall? Discuss…

** Any resultant reduction in spread and severity of forest fires is to be welcomed because there is evidence that globally-elevated CO2 levels are encouraging greater vegetation growth that reduces streamflow – water from which source may be necessary to extinguish the fires (Anna Ukkola et al.).

*** Or imagine the reluctant arsonist’s autobiography entitled, “No burning ambition”..?