Monday, 24 July 2017

The nature of landscapes

The wildlife present in any given landscape is determined by the characteristics of that landscape, but what are the characteristics that are most influential, especially for farmland species where the conflict between profitable food production and wildife conservation has played out most forcefully over the past half century or so?  These influences could be types of crops or the amount of semi-natural habitats, or the diversity of different crops and semi-natural habitats, or the complexity of the spatial arrangement of those crops and semi-natural habitats across the landscape.   Inevitably, different species are dependent on cropped or semi-natural habitats to differing extents, but the diversity or spatial arrangement may play an additional role.

Landscape diversity (left) and complexity (right)
We know that some bird species are associated with woodland, others with open fields, and still more use a combination of open fields and woodland or hedges.  Our monitoring at Loddington also tells us that different bird species are associated with different crops, with linnets and reed buntings using oilseed rape, and tree sparrows using field beans for example.  How crops are managed is another influence.  Low input crops support a greater abundance of invertebrate food for breeding birds than intensively managed crops for example. Twenty years ago, our research at Loddington showed that yellowhammers gathering food for their young used different crops at different times during the breeding season.  They had a foraging range of up to 300 metres, so both crop diversity and spatial arrangement of habitats would influence their access to suitable foraging sites.  
Fallow land with Holm Oaks in the study area
In a recently published paper, we explored the influences of landscape characteristics on bird communities in an agricultural area of southern Portugal.  Modelling used bird survey data from 1995-1997, and a subsequent period (2010-2012) in which changes to landscape characteristics had occurred as a result of Common Agricultural Policy reform.  For both farmland species, and rarer species that are characteristic of open steppe conditions, the heterogeneity of natural habitats had some positive influence, and for farmland species, the amount of edge had a positive effect.  However, for the steppe birds, the greatest positive influence was the area of rain-fed arable crops and pasture.

These results suggest that, while structural characteristics of the landscape have an influence on breeding bird communities, the land that is used for food production can have a greater influence for some species if managed sympathetically.   Southern Portugal is not the same as the UK, but this paper supports the suggestion that we need to consider both the composition of the landscape - the crops we grow and the way we grow them - as well as landscape heterogeneity to meet the needs of farmland wildlife. 

This is an approach that we are taking at Loddington, where we have increased habitat diversity and complexity by introducing new habitats through our Environmental Stewardship agreement, but have also increased the diversity of cropped land by extending the arable rotation to include more crops.  To some extent this change is driven by the need to manage competetive grass weeds, but this approach makes the practical management of the rotation more complicated, demands a greater knowledge base, and requires greater storage capacity for the different harvested crops for example. In the past, we have increased the complexity of the spatial crop distribution across the farm, as well as the diversity, but this proved to be a step too far in terms of the economic cost to the business.

We also modify the management of our crops, not least by the selective use of pesticides to minimise negative ecological impacts on pollinating insects, invertebrate predators of crop pests, and the invertebrates that provide food for farmland birds.  Such an approach also requires commitment and knowledge and complicates farm management decisions in what is already an economically challenging world.  The global market for crops pays little heed to the requirements of wildlife, or farmers wishing to conserve it.  Similarly, our move, over a number of years, towards a no-till system of crop establishment, stabilises soil conditions, contributing to better soil function, with potential benefits to terrestrial and aquatic wildlife, but it is not without its challenges and economic costs along the way.

Modifying crop management, increasing crop diversity, and increasing landscape complexity are all changes that are likely to benefit wildlife and landscape in the UK as much as in southern Portugal, but the farming systems and approaches to achieve this are very different.  That is something to consider between now and March 2019.


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