'99 Update

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Wildlife & Habitats

Introduction

Biodiversity (the variety of life on earth) depends on a delicately balanced environment. Indeed our own health and quality of life is closely linked with the well-being of the habitats and wildlife around us. In Hertfordshire, we are helping to maintain this variety through the Biodiversity Action Plan (BAP) which details targets and actions for key species and habitats.

Indicator 1: Population of Water Voles

The presence of water voles is an indication of good water quality and healthy river bank-side habitats. Threats to water voles include habitat loss, fluctuations in water levels, predation and pollution. 100 monitoring sites have been established by the Hertfordshire Biological Records Centre (HBRC); the aim being to survey 25 each year. This year evidence of water voles was found at 16 of the 25 sites investigated. Two of these sites were stretches of river which water voles had re-colonised since 1996. Of the sites where no water voles were detected, one had been a positive area for this species in 1996.

Indicator 2: A Sample of Key Bird Species

By agreement with the British Trust for Ornithology (BTO), three key indicator species of birds have been selected for Hertfordshire. Survey data has been collected over three seasons. An index of percentage change year-on-year has been calculated by the BTO, both at a national level, and now, specifically for Hertfordshire.

Skylark (indicative of the 'health' of the farmed landscape)
The Skylark is on the national Red List of birds of conservation concern, owing to a steep decline in its numbers across the country. This is considered to be owing to major changes in the management of arable farming. The national index between 1994-98 was -5. Hertfordshire figures showed a -4 figure for 1995/96, -7 for 1996/97 and +20 for 1997/98. This shows that the number of skylarks in Hertfordshire has gone up where nationally they have declined.

Song Thrush (reflecting trends within urban and suburban landscapes)
The Song Thrush is also on the Red List of birds of conservation concern owing to a long-term and very substantial decline in its populations nationally. From being one of the commonest garden birds, it is now quite scarce, although still widespread. The national index for 1994-98 is -1. In Hertfordshire it was +4 in 1995/96, -18 in 1996/97 and +6 in 1997/98. The recent increase in Hertfordshire is welcome, but not yet statistically significant. Nationally, the population is at an historically very low level. Poor winter survival owing to reduced food availability; poor chick survival owing to summer droughts; and reduction in the kind of scrubby habitat generally needed for breeding have all been identified as possible causes.

Willow Warbler (reflecting changes in woodland species communities)
The Willow Warbler is a summer migrant that winters south of the Sahara, and depends on young scrub or regularly coppiced woodlands for breeding. It was the most widespread and abundant warbler species until recently, but has been showing a marked decline locally in recent years. Nationally it has shown an upward population trend of +25 for 1994-98, but in Hertfordshire it was -7 in 1995/96, -24 in 1996/97 and -7 in 1997/98. The difference between trends nationally and locally would suggest that its local problems are not due to changes in its wintering grounds or on migration. Possible reasons could include food shortages in drought years or reduction in habitat quality and extent as woodlands in Hertfordshire have ceased to be managed.

Indicator 3: The number of Wildlife Sites in Hertfordshire

The total number of Wildlife Sites identified in Hertfordshire at September 1999 was 1774. During the last year 13 Wildlife Sites are known to have been lost across the county: 4 have been destroyed by development, 3 have been ploughed and 6 have lost their ecological interest or been degraded.

40 new Wildlife Sites have been selected, mainly on the basis of new data coming into HBRC. The majority of these sites are in North Herts District, and one is in Hertsmere Borough. These new sites are now in the revised local plans for these two authorities, along with the other Wildlife Sites.

Number of Wildlife Sites per District/Borough

Monitoring the Natural Environment

If you would like to know more about these or other natural environment monitoring get in touch with the contact below.

For further information contact: Trevor James, Biological Records Centre, Hertfordshire County Council, 01992 555220