Posted by: Dan | August 20, 2009

Measurable Losses of Biodiversity in Europe

Those who read here often know that one of my primary concerns for birds here in Cyprus is the very high levels of poaching, and the subsequent impact of this over-exploitation on biodiversity. As such I was struck by a 2008 study by Stuart Butchart in Bird Conservation International. The article, titled “Red List Indices to measure the sustainability of species use and impacts of invasive alien species,” was done in coordination between BirdLife International and the International Union for Conservation of Nature (IUCN).

Evidence of utilisation by humans was found for a total of 4,561 bird species, representing 45.7% of the world’s 9,990 extant and extinct bird species. Excluding historical uses and those species for which trivial numbers of individuals are involved gives a total of 4,173 species (42.3% of 9,856 extant species). Among these, two purposes of use dominate: 3,649 species (37.0% of extant species, 87.4% of utilised species) were recorded as being used as pets, and 1,398 species (14.2% of extant species; 33.5% of utilised species) were recorded as being hunted for food (Fig. 1). Less significant uses include sport hunting, wearing apparel or ornamentation and medicine (usually traditional), with trivial numbers of species being recorded as used for handicrafts, fuel (from oil or fat, principally from seabirds) and household goods (e.g. down for mattresses), etc. Many species are used in more than one way; for example, 68.9% of species that are hunted for food are also kept as pets.

It’s a thorough report, that then goes on to statistically evaluate the fate of species according to Red List Indices (RLI’s), a statistical metric of how much a given factor contributes to worsening conservation statuses. RLI’s for birds under threat by hunting or trapping, and by invasive species, do not show a significant downward trend as compared with other birds. The result is that, by themselves, these factors are not a significant threat to biodiversity loss.

The trouble is that, as we know, there are a number of factors attributed to species loss.

Well, looking at the trends for the bird’s of the world (as reported by BirdLife’s 2008 State of the World’s Birds report) has been as follows:

A total of 153 bird species is believed to have become extinct since 1500. Avian extinctions are
continuing, with 18 species lost in the last quarter of the twentieth century and three more known or suspected to have gone extinct since 2000.

The IUCN Red List for Endangered Species lists a further 192 species that are critically endandgered and at imminent risk of extinction. As many as 40 of these are suspected of being extinct, but have had recent unconfirmed sightings.

Of the extinct species, 138 out of 153 have been island endemics – their range was limited even before humans arrived. The situation is exemplified by Hawaii, where 30% of all known recently extinct bird taxa originally lived. Other areas, such as Guam, have also been hit hard; Guam has lost over 60% of its native bird taxa in the last 30 years, many of them due to the introduced Brown Tree Snake.

And of the 15 continental bird species to have gone extinct since 1500, several of them are famous for the apocalyptic degree to which they were hunted or their habitat destroyed. The Carolina Parakeet, Ivory-billed Woodpecker, Eskimo Curlew, Columbian Grebe, Bachman’s Warbler, and of course the Passenger Pigeon.

Of the 192 critically endangered bird species, again, the majority are island endemics. To highlight the European region however, the Slender-Billed Curlew population is thought to be down to only about 50 adults, primarily due to excessive hunting on its Mediterranean wintering grounds. Sociable Lapwing is also rapidly declining – currently at 20-25% of 1930 population levels and thought by some to decrease another 80% in the next decade, mostly due to habitat loss. The Bald Ibis also, while common in zoos, exists with ~95% of its population now restricted to Morocco, due to hunting, loss of foraging habitat, and pesticide poisoning.

And of endangered (but not ‘critically endangered’) birds that can be seen here in Cyprus on occasion, there is the Audouin’s Gull, Egyptian Vulture, Saker Falcon, and White-headed Duck.

For Cyprus, the threats are no different. Rapid development on the coast is destroying habitat, like the Oroklini marsh, of which large portions have been drained for the construction of housing developments. Millions of passerines are trapped or shot each year as well. What is the impact here?

As noted, statistics show that while hunting such as that of the scale of the Passenger Pigeon in the 19th century is devastating, hunting and trapping at current levels is not – at least not by itself. The problem with current poaching, at least in Cyprus, is that it pushes rare species to become rarer still. It only makes sense that habitat destruction and poaching – direct and indirect causes of bird mortality – would contribute to the observable declines of common birds of Europe [.pdf].

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