Pop That Cork
Rise of plastic corks threatens Mediterranean bird habitat
That Merlot with the plastic bottle-stopper may be threatening biodiversity, according to a new study of bird life in the Mediterranean oak forests that produce traditional corks.
“Montados” in Portugal and “dehesas” in Spain are agricultural grasslands dotted with the cork oak (Quercus suber) and holm oak (Quercus ilex) trees. The cork oaks produce much of the pithy bark that keeps fine wines from spilling and spoiling. In a centuries-old tradition, cork makers take long strips of bark from the oaks every 9 years, starting when the trees are about 25 years old. The bark then regenerates. But cork forests do more than just provide jobs for nearly 100,000 people, Ana I. Leal of the University of Lisbon and colleagues note in Biological Conservation. Montados, for instance, “are very important for Mediterranean birds.”
Exactly how debarking influences bird biodiversity, however, hasn’t been carefully studied. To fill that glass, in 2008 Leal and her colleagues surveyed birds and arthropods (including insects) at a large cork forest in Portugal. In particular, they examined how bird abundance and density differed between trees that had recently been stripped, and those that had had up to 9 years to recover. In all, they counted 63 species of birds in the study area in spring, and 56 in winter. They also collected a total of 25,582 arthropods in spring, and 10,804 in winter.
Overall, they found that cork age didn’t influence species richness, but that areas with recently debarked trees tended to have slightly lower bird densities. They also found that one group of birds – “gleaners” that pick their prey out of bark crevices – tended to be a bit less common in recently debarked areas. At the landscape and regional scales, however, these debarking impacts were slight: “In fact, even for bark gleaners, the exploited montados are still the most favorable habitat available in the study region,” the authors note.
The real threat to the birds, they write, is “growing competition between cork stoppers and synthetic bottle stoppers. In fact, without the high income resulting from the production of cork stoppers montados may lose their economic viability. This may result in its replacement by other types of land cover, much less valuable for birds and for other components of biodiversity.” To keep the cork forests intact, they conclude, rural residents will need “clear signs… that their land is economically, ecologically and culturally valuable and viable using traditional land management practices.”
Perhaps a toast, then, to keeping the cork in the bottle? – David Malakoff | March 28, 2011
Source: Leal, A.I., et al. Impact of cork extraction on birds: Relevance for conservation of Mediterranean biodiversity. Biol. Conserv. (2011), doi:10.1016/j.biocon.2011.02.021
Image © Stefan Ataman | Dreamstime.com
