We are pleased to announce that the next Editor’s Choice will be The ancient forests of La Gomera, Canary Islands, and their sensitivity to environmental change by Nogué et al. This paper will be free to access when 101: 2 is published online.
Editor’s Choice 101:2
While this Editor’s Choice “The ancient forests of La Gomera, Canary Islands, and their sensitivity to environmental change” was being edited in October 2012, fires broke out in the Garajonay National Park within a few km of the study site. The fires burnt 18% of the 4000 ha Park and were widely reported in apocalyptic terms as an ‘ecological disaster’ and a ‘severe threat to a UNESCO World Heritage area’. But was this the case? Sandra Nogué and colleagues provide evidence that should promote a rethink of the role of fire in these islands.
La Gomera, a small, rugged, volcanic island, presents an interesting variant on the theme of island vulnerability. Before humans, it had no mammals except for bats, but there were extensive palm and laurel dominated forests widely believed to be remnants of a once widespread Miocene subtropical forest. Settlement of the island by the North African Guanche, about 2500 years ago, forest clearance for agriculture, and the introduction of goats, pigs and rodents, fundamentally changed the dry lowlands. Nevertheless, the laurel and heath ‘monte verde’ forest associations of the mist-drenched uplands survived intact through later Hispanic settlement in the 15th century and the onset of modern tourism. The questions conservation managers pose are the usual ones: What was the original state of these upland forests? How resilient are they? Is climate change a threat? This palaeoecological investigation of a few metres of clay sediments in a small, dry, basin near the summit of Garajonay National Park on La Gomera provides some surprising answers.
The first surprise revealed by this study is that the major alteration of the upland forest happened long before human settlement, when a laurel-palm association was largely replaced by heath forest, a change driven by drier climates and natural fires. The second surprise is that settlement had little effect on the forest. Granted, there were large fires during the human era, and grazing (shown by the increase in Sporormiella spores), but they produced little change in the vegetation. And, finally, the Hispanic conquest accompanied a dramatic decrease in fire, possibly a result of the indigenous population abandoning the uplands.
What are conservation managers to make of this? The major lesson is that these are not fragile ecosystems. In this the palaeoecology strongly supports previous work. Some of the dominant trees are now troublesome invaders elsewhere in the world. Nitrogen-fixing Morella faya (also known as Myrica faya) has been transforming ecosystems on that other iconic, volcanic, oceanic archipelago, Hawai’i (Vitousek and Walker 1989). Phoenix canarensis, the Canary date palm, is now considered a conservation weed in Australasia. Unusually for oceanic islands, the La Gomera forests are well adapted to fire (Höllermann 1993). For example, Pinus canariensis is rarely killed by fire as it has a thick, heat-resistant bark, it resprouts, and has serotinous cones. Quick recovery of vegetation ensures little nutrient loss and possibly even a rejuvenation of soils.
Fire devastates the economy of La Gomera, not the forests. The moist upland forests are not easy to burn and tolerate fire. However, fascinating though regenerating forests are for ecologists, blackened landscapes have little attraction for nature tourists, a major source of income. Very few fires in the Canaries are natural; most are human in origin (Höllermann 2000). The October fires were lit by arsonists, or ‘ecoterrorists’ as they have been termed. The immediate challenge to the management of these unusual islands is not the approach of climate change, but the environmental pressure exerted by a growing population (+23% since 2000) and vandalism by alienated individuals.
Associate Editor, Journal of Ecology
Höllermann, P. (2000) The impact of fire in Canarian ecosystems 1983-1998. Erdkunde 54: 70-75.
Höllermann, P. (1993) Fire ecology in the Canary Islands and central California – a comparative study. Erdkunde 47: 177-180.
Vitousek, P.M. & L.R. Walker (1989) Biological invasion by Myrica faya in Hawaii – plant demography, nitrogen fixation, ecosystem effects. Ecological Monographs 59: 247-265.