A Common toad colony migrating across a road near Ipswich. "We patrol the crossing, and collect and move them to their breeding ponds. This is a male in amplexus with a female, and another male alongside." Photo: Dave via Flickr (CC BY-NC-SA).
Toad's 30-year decline shows 'large-scale deterioration of environmental quality'
6th October 2016
A 30-year decline in toad populations recorded by volunteers, shows the need to rebuild vital 'green infrastructure' across both the wider countryside and urban areas, writes Oliver Tickell: reversing habitat fragmentation, digging out ponds and ditches, and leaving ample unkempt areas for cover and hibernation.
It is not sufficient to protect habitats of rare specialists. Conservation efforts need to focus more on generalist widespread and common species and the countryside as a whole if system function and resilience are to be maintained.
A new study led by conservation charity Froglife reveals a steep 30-year long fall in populations of the common toad.
"Given the declines, this common species almost qualifies for International Union for the Conservation of Nature (IUCN) red-listing over this period despite volunteer conservation efforts", state the scientists. "Reasons for the declines and wider impacts remain unknown."
The data underlying the study has been gathered by 'crowdsourcing' with thousands of conservation volunteers in both the UK and Switzerland submitting figures on the numbers of toads in their areas.
Every year thousands of volunteers in the UK, working as part of Froglife's 'Toads on Roads' patrols, help save amphibians as they migrate to their breeding ponds across busy roads. Toads are particularly vulnerable to traffic and over 800,000 are carried to safety by volunteers each year in the UK and Switzerland.
Froglife's conservation scientists teamed up with Swiss counterparts to analyse millions of records of common toads (Bufo bufo) collected by these patrols over more than three decades from the two countries.
Unfortunately, despite the effort of the volunteers, the researchers show that our toads have undergone huge declines. On average common toads have declined by 68% over the last 30 years in the UK. In some areas, such as the south east of England, declines have been even more pronounced.
30 years of continuous decline
The team's results, published in the open-access journal PLOS ONE, show that toads have declined rapidly and continuously since the 1980s in both countries. It is likely that hundreds of thousands of toads have disappeared from the countryside in the past 30 years.
In the UK, south east England suffered the worst declines while in the west (including Wales, south west and west England) populations also declined but have remained stable for the past decade. The North, including northern counties and Scotland, has also seen significant toad declines in the past 20 years.
It is not clear what has caused numbers of toads to drop so dramatically but likely causes are a combination of changes to farming practices, loss of ponds, an increase in urbanisation and more deaths on roads as traffic values have increased. Climate change could also be a factor as research has shown that milder winters are detrimental for hibernating toads.
Dr. Silviu Petrovan, Conservation Coordinator at Froglife and one of the authors of the study said: "Toad declines at this scale over such large areas are really worrying. Toads are extremely adaptable and can live in many places ranging from farmland and woodland to suburban gardens.
"They are also important pest controllers eating slugs, snails and insects and are food themselves for many of our most likeable mammals such as otters and polecats." And he emphasised the essential role of members of the public both in toad conservation, and in making the study possible:
"Without the efforts of the thousands of volunteers that go out and move amphibians across busy roads we would have no idea that these declines had occurred and the situation could be much worse. One thing that is clear is that we need to do more to look after our environment in order to protect the species that depend on it."
'Conservation is not just for special sites and rare species'
As the authors note in their paper, the long-term and ongoing decline of one of Europe's most common amphibians is "a significant cause for concern and has unknown wider impacts." However the decline "has been uncovered almost incidentally given the lack of specific long-term monitoring data for common amphibians."
They also highlight the increasing trend of sharp population declines of once common species. For example, house sparrow and hedgehogs, one common across the UK, are also becoming increasingly rare, suggesting "a large-scale deterioration of environmental quality."
Recent declines of common species could be explained by the fact that "common species occupy areas of land mostly outside of protected areas, including for the common toad, farmland and semi-urban areas", the scientists report. "Their declines could be linked to the general deterioration and fragmentation of the quality of the environment on a landscape scale and which cannot be offset by smaller improvements elsewhere, such as in well managed reserves ...
"Although conservation goals have moved towards a more wide-encompassing approach that incorporates ecosystem goods and services, this requires a shift in conservation practice that makes it clear that it is not sufficient to protect habitats of rare specialists. Conservation efforts need to focus more on generalist widespread and common species and the countryside as a whole if system function and resilience are to be maintained."
Countering habitat fragmentation
Paul Edgar, Senior Amphibian and Reptile Specialist from Natural England, the government's wildlife advisor which has funded Froglife's road mitigation research, said: "This paper highlights a number of important issues for our native amphibians and conservation more generally in the UK. The common toad is sadly on a downward trend.
"This is partly because of habitat fragmentation, and so understanding and mitigating the impacts of this issue is vital. We need to continue to build good quality habitat links across the wider landscape if we are to offer opportunities for this species to recover. We're working hard to do this through measures such as Countryside Stewardship in the rural setting, and ensuring good quality Green Infrastructure is included in new developments.
"This paper reinforces the vital positive role that the public play in both protecting and recording data about our wildlife. We need to build on this engagement to further help us collaboratively reverse these declines as a matter of urgency."
Members of the public can also help conserve toads and other wildlife by improving habitat in their own gardens and local areas: by digging out ponds, for example, and leaving areas of rough, untended vegetation where toads, frogs and newts can hide out in the day and hibernate in winter.
Oliver Tickell is contributing editor at The Ecologist.
The paper: 'Volunteer Conservation Action Data Reveals Large-Scale and Long-Term Negative Population Trends of a Widespread Amphibian, the Common Toad (Bufo bufo)' is by Silviu O. Petrovan & Benedikt R. Schmidt, and published in PLOS ONE (open access).
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