Research


Interactions between agricultural management, biodiversity and life history:
Insectivorous mammals and their prey as bioindicators

Funded by Defra (the UK government's Department for Environment, Food and Rural Affairs) and English Nature (now part of Natural England). December 2002-December 2006.

(Previous members) Dr Nancy Jennings and Dr Michael J.O. Pocock
Mammal Research Unit and Bat Ecology and Bioacoustics Lab


poppies in field
© Mammal Research Unit
As agriculture has become more
intensive many plants and animals
have become rarer

How can we work out what effect agriculture has on wildlife?
How can we tell whether agri-environment schemes are working?

The ideal way to find out the effect of agriculture or agri-environment schemes on biodiveristy is to assess the abundance of all biodiversity, including mammals, birds, insects, plants, fungi and bacteria. This is completely impractical in almost all cases. An alternative approach is to use biotic indicator taxa.

Bioindicators

A biotic indicator taxon (also called a bioindicator, which could be a species, or group of related species) is one that is sensitive to the factors that affect overall biodiversity. Therefore, by measuring the relative abundance of the indicator taxon we can assess the overall effect on biodiversity.

Our study

In this project, we studied shrews, bats, and their prey as potential biotic indicators of habitat change due to agricultural intensification. We:

  1. quantified the effects of various aspects of farm management on populations of insectivorous mammals and their prey
  2. calculated a numerical index of sensitivity for each taxon, so that the most sensitive taxa, and therefore those most suitable as biotic indicators, could be identified
  3. explored the ecological traits underlying variation in the indexes
hedgerow
© Mammal Research Unit
We found that
field boundaries are
very important for
biodiversity

We selected four key aspects of agricultural intensification (increased use of agrochemicals, the switch from hay to silage, boundary loss, and the reduction in habitat diversity) and tested the sensitivity of the animals to each aspect.

Our findings

We found substantial variation in the sensitivity of taxa to three aspects of agricultural intensification. Groups with significant sensitivity to increased agrochemical inputs included Carabidae (ground beetles), previously suggested as indicator taxa in farmland, and Diptera (flies). The switch from hay to silage had a positive effect on many beetles, but had a substantial negative effect on Hepialidae (a family of moths). The mammals (shrews and bats) were not significantly sensitive to agrochemical inputs or the switch from hay to silage, but were strongly sensitive to boundary loss.

What makes animals sensitive to habitat change?

We wanted to understand why certain taxa are more sensitive than others. We explored relationships between our measures of sensitivity and ecological and life history traits (such as body size, mobility and fecundity), and found that some traits explain variation in sensitivity and so can be used to pre-select biotic indicator taxa for testing of sensitivity. Understanding which traits are related to sensitivity is vital, as sensitivity to habitat change is important in determining a taxon's ability to survive in dynamic environments.


a fielf of hay
© Mammal Research Unit
Many grass fields are now managed for silage,
but we found that some moth species were
much more abundant in hay fields

Conclusions

We conclude that of our study taxa, Carabidae (ground beetles), Diptera (flies) and moths are the most sensitive biotic indicators of agricultural intensification. They are also accurate and repeatable to survey at the temporal and spatial scales required. Our study also allows the evaluation of habitat management options likely to benefit the conservation of the study taxa. Entry Level Stewardship (ELS) has recently been introduced by Defra with the aim of positively affecting biodiversity. Several ELS options (options for boundary features, arable land, and lowland grassland) are highly likely to benefit their populations in agricultural land. The conservation management of boundary features is more beneficial than field management for most of the taxa we considered.

The full findings of our study will soon be published in peer-reviewed scientific journals and will be available on the Defra website in due course.

Contact details

Dr Nancy Jennings
1 Mendip Villas
Crabtree Lane
Dundry
Bristol BS41 8LN, U.K.

Telephone: 0117 9780696
E-mail: Nancy Jennings

Dr Michael J. O. Pocock
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG, U.K.

Telephone: 0117 9545960
Fax: 0117 3317985
E-mail: Michael Pocock