Hedge management for nesting birds

The British lowland countryside is characterised by a network of hedges, a much valued component of our cultural landscape and a nesting habitat for countless birds.  Together with RSPB partners, we recently published a paper on the effects of hedgerow structure on the nesting success of these birds.  Our previous research at Loddington revealed that controlling crows and magpies had a beneficial effect on nesting success and subsequent breeding numbers of some species, and also that nesting success was influenced by the structure of the habitat in which nests were located.

As management of many hedges has been neglected in recent years, resulting in a more open structure, this could leave nesting birds more susceptible to predation than in the past.  Our monitoring of 399 nests over two years revealed that birds were choosing the denser parts of hedges in which to nest.  Nest survival was higher in hedges that had been cut four years before than in those that had been cut more recently (in the previous year), and nests fared better in mechanically trimmed, stock-proof hedges than in recently laid or neglected leggy ones.

This is encouraging.  While we have shown that the control of crows and magpies can have an important role to play in songbird conservation where landscape characteristics support high numbers of these species, our recent research shows that hedgerow management can also help to improve songbird breeding success on farmland.

Farming and flooding - investigating common ground

Payments to farmers are currently under review as a result of our forthcoming departure from the EU.  It will ultimately be up to the UK government to decide what farmers get paid, or more importantly perhaps, what they get paid for.  Leaving aside the production of abundant, affordable and nutritious food, what do UK tax payers expect from farmers in return for their financial support?

Through the life of our EU membership, wildlife conservation has been a primary focus for agri-environment schemes, and this continues to be a major concern for a substantial proportion of the population.  Landscape is another.  An abundant supply of clean drinking water is a fundamental requirement of the population as a whole and becomes increasingly challenging as that population increases, and changes in rainfall patterns influence reservoir storage.  Most recently though, it has been the frequency of major flood events that has risen up the popular and political agenda.

Farmers are also concerned about the increased frequency of intense storms in recent years.  Apart from the flooding of low lying farmland, intense storm events cause water-logging and compaction of soils which, in turn, result in deterioration in soils, increases in weed burdens, reduced crop yields, and increases in input costs.  All of this reduces both farm profitability and the production of our food.  Getting water off the land through improved drainage is an increasing priority for many farmers.

So what can farmers do to reduce, rather than accentuate flood risk downstream?  Over the next five years, we will be addressing this question as part of our research in the Water Friendly Farming project, a landscape scale experiment with the Freshwater Habitats Trust which started in 2012 and involves three headwater catchments. 

Diagramatic representation of headwater ditch or small stream showing the two opportunities for controlling flow during storm events - optimising soil management to improve its buffering capacity, and creating permeable timber dams.

While effective drainage on our clay soils is essential, there is scope to improve the water holding capacity of the soil above the level of the field drains.  Improved soil management that reduces compaction and increases organic matter and biological activity improves conditions for crops, but also increases the capacity of the soil to hold water when it rains. Even greater benefits can arise from reduced soil erosion because of the associated reduction in sedimentation of drainage channels downstream.  This is all very much easier to say than to achieve in practice, but we are providing farmers with whatever support we can to help them achieve this over the coming years.  In doing so, we can draw on our own practical and research experience at Loddington, and on specialist advice from others.

We have already been surveying some fields for soil compaction, organic matter and earthworm abundance, all of which influence both flood risk and crop performance, and sharing this information with farmers.

Recently constructed permeable dam in the Water Friendly Farming project study area

There is also scope for holding back water in ditches and small streams by using permeable dams.  Such dams can often be relatively simple to install and permit water to flow normally uderneath them for most of the time, but hold it back when the water level rises during heavy rain.  Retaining water in headwaters, even if only for a couple of hours, can reduce flood risk downstream.  We have just started installing such dams in one of the two treatment catchments in our Water Friendly Farming study area, using locally sourced timber and a local contractor. 

We are using a combination of hydrological modeling by Colin Brown at York University, on-site observation, and guidance from catchment farmers to inform the siting of the dams.  The objectives are always to maintain base flow, optimise water storage during storms, and avoid impacts on productive land.

Over the coming years, we will continue to provide whatever support we can to help farmers in the study area to improve soil management, and we will install permeable dams where it is feasible and effective to do so.  By continuing to monitor flow at the base of the three study catchments, and comparing these data with data already collected as part of our ongoing research, we will be able to evaluate the effectiveness of this approach in terms of reduced downstream flood risk.  Such data, and our experiences along the way, will help to inform the development of policy that enables farmers to be rewarded for carrying out work on their land which has benefits for people living far beyond the farm boundary.

Allerton Agroforestry

Identifying and understanding multiple benefits from single management practices has been at the heart of our research activity throughout the life of the Allerton Project.  There are few better examples of such multiple benefits than agro-forestry on marginal land.  A number of research projects across the country have explored its potential, but there has been no widespread adoption, in part because government land use policy has focused on single objectives associated with arable, pasture and forestry, and because of apparent limited application on productive land. Agroforestry systems are more widely accepted and adopted in many other parts of the world and I have been fortunate to conduct research into such systems in Portugal and West Africa, as well as following UK agroforestry research with interest.

Portuguese Montado is the classic agroforestry system with tree densities usually of 30-60/ha and multiple uses including cork and charcoal production, and shooting and wildlife conservation, as well as livestock and arable production.

We now have an opportunity to investigate the merits of agroforestry at Loddington.  A moderately productive pasture field that has been used for rearing lambs for many years has been planted with trees at a range of densities.  While maintaining lamb production from most of the pasture through our collaboration with Launde Farm Foods, the trees bring potential additional benefits. The tree species selected, and the inclusion of shrubs in some places, are specifically intended to improve the area for pheasant shooting. The trees and shrubs also provide a new wildlife habitat.  Through the influence of trees on the soil, we might expect increased carbon sequestration, enhanced soil biology and potential for flood peak attenuation through improved infiltration of water during storms.

The trees have been planted without support from an agri-environment scheme but with help from the Woodland Trust who are also supporting our research.  Two plots are planted with trees at a density of 100/ha to represent a relatively high agroforestry density, and these will be compared with other plots at higher tree densities.  Some are planted at 400/ha to represent the lowest permissible density for open woodland planting with government funding, and others are planted at 1,600/ha, the maximum density that can normally be funded for woodland creation.  Trees will be thinned in due course as part of the normal management of such a plantation, but differences in tree density will be maintained.  We anticipate very different results across this range of tree densities in terms of the trade-offs and synergies between our various economic and environmental objectives.

The next few years provide us with an opportunity to learn much about the management of the plots to meet our multiple objectives, and we will also be gathering data to help inform this process.  Our initial priority is to gather baseline data on grass yield and lamb production, tree canopy area, bird numbers, and soil biology, organic matter, compaction and infiltration. These data will ultimately enable us to make environmental and economic assessments of tree planting on pasture under a range of scenarios, and recommendations for future policy and practice elsewhere.

As the trees develop, we will explore the interactions between a range of objectives such as livestock production, carbon sequestration and flood risk management in relation to different tree planting densities.