Birds could signal mass extinction

4 October 2010

The first detailed measurements of current extinction rates for a specific region have shown that birds are the best group to use to track the losses. The study also reveals Britain may be losing species over ten times faster than records suggest, and the speed of loss is probably increasing: the losses from England alone may exceed one species every two weeks.
The study, by Oxford University researchers, shows that many types of obscure organism in Britain are going extinct at the same rate as the birds - evidence supporting fears of a global mass extinction. A report of the research is published in an upcoming issue of the journal Biological Conservation as countries prepare to meet in Japan 18-29 October to discuss biodiversity conservation targets.
'Biodiversity loss is arguably much more serious and more permanent than climate change,' said Clive Hambler of Oxford University's Department of Zoology, lead author of the research. 'But it's impossible to know if policy targets to reduce the loss are being met without accurate measures of extinction rates. Until now, we had only crude estimates for a very few types of organism. Now we've got evidence that many groups of living things - lichens, bugs, moths, fish, plants and so on - are going extinct at a very similar rate to the birds.'
Using Britain's uniquely detailed natural history records, the researchers found that 1-5% of the region's species in many groups were lost since 1800, with higher losses in the Twentieth Century compared to the Nineteenth. Using further data from the USA and across the whole globe, the researchers show that the patterns of extinction in Britain are likely to be typical of those found on land and freshwater elsewhere.
Mr Hambler said: 'The birds are beautiful creatures, but they are also diverse, and many of them are specialised to particular habitats. This makes them sensitive to changes in their environment - such as loss of mature trees, or the drying out of swampy ground, or coastal development. And what makes them really special for monitoring extinction is that they are also exceptionally easy to study, anywhere in the world - so we can detect declines in their populations long before we notice losses of the more obscure things like slime moulds or mosses. It's no coincidence they can signal environmental change.'
'The underlying reason for the similarity of extinction rates in birds and the other living things is that habitat loss affects them in the same way. Our work supports the use of birds to indicate extinction rates in Britain, the USA and globally, and they should now be tried in places such as tropical forests where the bulk of other species will never be recorded.'
'The recorded extinctions in any region are just the tip of the iceberg, because there are not enough observers,' said Mr Hambler. For example, in March this year the British government's advisory body, Natural England, reported about 500 species lost from England since 1800. 'The losses reported by Natural England are under 0.5% per century, from England's 55,000 species,' notes Mr Hambler. 'Our research suggests that the actual losses could be over ten times this number, with about one species going extinct in England every fortnight.'
Natural England also reported species losses in England had apparently declined in recent decades, but the Oxford study suggests that this is not the case. Hambler and colleagues found there are about 1000 endangered species on the brink of extinction in Britain - indeed many of these may already be extinct.
'People tend to be hesitant in declaring extinction, which leads to problems assessing the current rate,' said Mr Hambler. 'Many ancient and important habitats in Britain are threatened today because of human activity and population growth - whether it's an increase in water use, growing use of wood fuel, or the growth of urban sprawl. Despite conservationists' efforts it's very likely extinction rates will continue to rise in Britain and globally for many years. These losses will impact on human welfare, and I'd say conservation needs a profile and resources even bigger than climate change.'
Alongside studies of birds, the researchers believe that recording rates of habitat loss will provide a good, simple measure of some elements of biodiversity loss.
Mr Hambler said: 'This work strengthens the claim that the world is suffering a mass extinction. We can now be much more confident that across the planet the less conspicuous and less well-known species are going extinct at a similar high rate to that already witnessed in birds, fish and amphibians.'

For more information contact Mr Clive Hambler on +44 (0)1865 271124 or +44 (0)1865 776192 or email

Alternatively, contact the University of Oxford Press Office on +44 (0)1865 283877 or email

Notes for editors

  • Publication: The report is published in the journal Biological Conservation go to:
    [doi: 10.1016/j.biocon.2010.09.004]
  • Targets: Following the United Nations Conference on Environment and Development (the Rio Earth Summit) in 1992, 193 countries signatory to the Convention on Biological Diversity committed 'to achieve by 2010 a significant reduction of the current rate of biodiversity loss'. European governments have committed to halt the loss of biodiversity by 2010.
  • Progress and meeting to discuss future targets: It is widely believed by conservation biologists that these targets have not been met and the Oxford research is further confirmation of this suggestion. It has been suggested that new targets to be set when governments meet to discuss progress should include a halt to global extinctions in the next few decades. The meeting is in Nagoya, Japan, 18-29 October: For further details of the targets and progress towards them see:
    -Gilbert, N Biodiversity talks get under way. Nature (published online 25 Jan 2010). [doi:10.1038/news.2010.31]-Butchart S.H.N. (2010). Global biodiversity: indicators of recent declines.
    Science 328, 1164-1168. [doi: 10.1126/science.1187512]
  • Rates of extinction in North America were assessed mainly from Wilcove, D S (2005). How many endangered species are there in the United States? Frontiers in Ecology and the Environment 3, 414-420. [doi: 10.1890/1540-9295(2005)003[0414:HMESAT]2.0.CO;2]. Global rates were calculated mainly from data in Vié, J-C (2009). Wildlife in a Changing World - An Analysis of the 2008 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland, and using the IUCN Red List of Threatened Species:
  • About a third of mammals that are reported globally "extinct" are subsequently rediscovered, according to a paper by Diana Fisher due in Proceedings of the Royal Society, Series B. Hambler et al. find the proportion of species reported extinct in Britain that have been rediscovered varies greatly between the groups of organism, and often depends on the difficulties in recording them. Some "rediscoveries" in Britain may be recolonisations from the continent of Europe
  • Comparison with Natural England's results: In March 2010, Natural England released a report Lost life: England's lost and threatened species (Natural England, Peterborough, available online). This included about 500 species which have been found in England but then 'lost', and most of these are probably extinct since 1800. However, it includes several which are widely considered exotic or introduced, and is less cautious about declaring when a species is extinct. It implies at least two species becoming extinct per year, but does not estimate the upper limit (which depends on poorly-recorded groups such as flies, fungi and beetles). According to standard ecological theory, extinction rates in smaller areas such as England would be expected to be higher than in Britain as a whole.
  • The Oxford research considers the well-studied families amongst the flies and fungi, and shows they have rates similar to other well-studied organisms, reinforcing the case that rates are similar in most terrestrial and freshwater organisms.
  • The Oxford workers reach some different conclusions to Natural England because they look in greater detail at the dates, pattern and rates of loss of species in different groups, consider the large number of endangered species, and identify serious recording biases against declaring recent extinction. Using their newly calculated percentage extinction rate, the Oxford group can project the known losses to the bulk of British (or English) species, most of which have not been studied in detail. However, despite the different methods, Natural England's report shows some similar results to the Oxford research, particularly that habitat loss has been the biggest cause of loss, and that butterflies are not good indicators of the general rate of biodiversity loss (despite many claims that they are).
  • Examples of extinct British species: 1) The Blue Stag Beetle Platycerus caraboides. This beetle, last recorded near Oxford, about 1820, needed abundant dead wood. 2) The Orange Spotted Emerald Dragonfly Oxygastra curtisii was probably exterminated in the 1960s by sewage pollution of a river. 3) The Clifden Nonpareil Catocala fraxini. This large moth, which prefers mature aspen trees, became extinct in Britain in the 1960s but may now be recolonising from continental Europe.
  • The authors are in the Department of Zoology, University of Oxford:

    Mr Clive Hambler is Lecturer in Biological and Human Sciences in Hertford College, and is author of the textbook Conservation (Cambridge University Press, 2004).

    Dr Peter Henderson is a Senior Research Associate in the Department of Zoology, and a Director of the environmental consultancy Pisces Conservation Ltd. He is author of several books including Ecological Methods (Blackwell, 2000), Practical Methods in Ecology (Blackwell, 2003), Marine Ecology. Concepts and Applications (with Martin Speight, as below) and Freshwater Ostracods (Linnean Society, 1990).

    Dr Martin Speight is Reader in Applied Entomology and a Fellow of St. Anne's College, Oxford. He is co-author of several books including Ecology of Insects.  Concepts and Applications (2nd edition, Blackwell Publishing, 2008), Insect pests in Tropical Forestry (CABI Publishing, 2001) and Marine Ecology. Concepts and Applications (Wiley-Blackwell, 2010, co-authored with Peter Henderson).