Understanding ecosystem service trade-offs in agriculture

Agricultural intensification brings great societal benefits from food production, but also has unintended consequences for wildlife and ecosystem services. Future farmland management needs to produce food, maximise ecosystem services and allow wildlife to flourish.

RSPB's Hope farm, at the time of the wheat harvest

Overview

Since the middle of the 20th century, agricultural productivity has increased hugely. During this intensification, more inputs of fertilisers and agrochemicals and increased mechanisation have pushed up yields, but have also had unintended consequences for farmland wildlife, and other parts of the farmland environment. Diffuse pollution, the loss of soil and agrochemicals and their by-products to the wider environment, is a major side-effect of modern farming.

Whilst development of new techniques, such as more accurate application, non-inversion tillage and use of winter cover-crops can address diffuse pollution, the advent of agri-environment schemes (which provide funding to farmers and land managers to farm in a way that supports biodiversity and improves the quality of water, air and soil) has allowed another avenue to tackle direct and indirect impacts of modern farming. However, the climate impact of modern farming is proving an intractable problem. Modern yields and productivity are only possible through the use of fertilisers and crop protection products, and these have climate costs in terms of their production and application, as well as use. Arable farming has to balance production of food with providing a home for farmland wildlife and reducing impacts on other ecosystem services provided or influenced by farmland.

We are currently engaged in two projects examining the balance between these competing demands on farmland:

Grange Farm

Grange (Hope) Farm, the RSPB’s lowland arable farm in Cambridgeshire, is run as a conventional farm, producing commercial quantities of typical combinable crops: wheat, oil seed rape, field beans, barley, millet. Alongside this we use a variety of management techniques to improve the farm as a wildlife habitat. Grange Farm has been in the Entry Level of Environmental Stewardship since its inception in 2007, and has also been involved in agri-environment research since the society took ownership in 2000. Since 2000, the farmland bird index has increase over 250 per cent, against a background of continued farmland bird declines. Having established it is possible to produce food whilst maintaining healthy farmland bird numbers, we are interested in the impacts of this management on other ecosystem services provided or regulated by arable farming. Having established the trade-offs between production and wildlife and greenhouse gas emissions over the first 13 years of our management at Grange Farm (Field et al 2015), we are now working with the Centre for Ecology and Hydrology (CEH) and Agrii, seeking to find multifunctional solutions to agronomic problems typical of lowland cereal farming. Grange Farm is one site of a network investigating the effects of using rotational cover crops to help improve soil conditions and invertebrate food chains, as well as helping in controlling pernicious weeds.

Cambridge Conservation Initiative

In a second work stream, we have engaged in a number of separate but linked projects, in collaboration with the Zoology Department, CambridgeUniversity, investigating the relationships between farming and conservation. Specifically, we are looking at the spatial arrangement of land uses dedicated to these two competing aims, and its effect on wildlife populations, agricultural production and polluting externalities of farming. In 2013, we convened an expert workshop in Cambridge, to address the possible benefits of increased per-area production in the UK on releasing land for conservation and its knock-on effects for climate change mitigation. This work, funded by the Cambridge Conservation Initiative (CCI), was published in Nature Climate Change in 2016.

Objectives

Grange Farm

Examine the link between soil management techniques and soil invertebrate populations
Characterise the nature of any relationship between soil invertebrates, vegetation structure and bird foraging
Establish the extent of benefits of management techniques (cover crops/compost addition) for weed suppression and crop performance

Cambridge Conservation Initiative

Establish the relationship between farming intensity and bird populations in UK landscapes
Establish what can realistically be demanded from agricultural production systems in terms of 'sustainable' production

Key Dates

Grange Farm

Autumn 2015: established a three-field two way replicated field trial of urban compost addition and rotational cover crop usage and sampling protocols for soil invertebrates and microbes, weed burdens and crop yield
Autumn 2017: establish links with Agrii and CEH to link our farm trial with other similar trials on other farms, and to enable microbial analyses

Cambridge Conservation Initiative

Summer 2016: appoint post doctoral researcher to facilitate UK land sparing/sharing project (Dr Tom Finch)
Autumn 2016: appoint post doctoral researcher to facilitate 'No such thing as a cheap lunch' (Dr Rowan Eisner)
Spring 2017 : Convene four-day international expert workshop in Cambridge to establish protocols and collect data for 'No such thing as a cheap lunch' analysis

Progress

Grange Farm

We have developed a multifactor spatial database of all cropping and agronomy at Grange Farm, and used this to compare actual productivity, predicted greenhouse gas emissions and agri-environment management with modelled yields and emissions under a series of hypothetical management scenarios aimed at maximising productivity. Initial work on this by Rachel Hill, an MSc student at the University of East Anglia, was completed in autumn 2013.

Cambridge Conservation Initiative

Convened a workshop with experts in relevant disciplines in order to develop scenarios of future agricultural systems in the UK

Planned Work

Grange Farm

Third annual invertebrate and soil sampling campaign, in June 2017
Microbial analysis of soils from different treatments - CEH
Identification of soil active invertebrates from different treatments - University of East Anglia MSc student
Measurment of soil mechanical properties and bird usage of different treatments - University of Leeds PhD student

Cambridge Conservation Initiative

Collection of data on yield and pollution rates for different agricultural techniques producing the four commodities of interest

Results

Grange Farm

We assessed the effects of different management priorities (production-driven cropping vs. wildlife-friendly farming) at Grange Farm on food production, greenhouse gas (GHG) emissions and biodiversity.

We modelled one actual and three alternative cropping scenarios using actual yields from the farm during 13 years, to calculate total yields and those foregone for agri-environmental measures. We measured crop yields, relative abundance of 19 farmland bird species, and CO2 and N2O emissions related to crop production.

Removing up to 10.5 per cent of land from production coupled with a more diverse rotation (including legumes) resulted in a large increase in breeding birds (177 per cent) and reduction of 9.4 per cent in GHG emissions at the cost of 9.6 per cent of food energy. Food protein lost was only 2.9 per cent. A smaller increase in bird numbers of 50 per cent could be achieved at a much smaller cost to yield (~1.7 per cent energy or protein) but with correspondingly smaller emissions reductions (1.2 per cent).

Cambridge Conservation Initiative

During the CCI and sparing/sharing and climate mitigation project, we assessed the technical mitigation potential offered by land sparing—increasing agricultural yields, reducing farmland area and actively restoring natural habitats on the land spared. Restored habitats could sequester carbon and offset emissions from agriculture. Using the UK as an example, we estimated net emissions in 2050 under a range of future agricultural scenarios.

We found that a land-sparing strategy has the technical potential to achieve significant reductions in net emissions from agriculture and land-use change. Coupling land sparing with demand-side strategies to reduce meat consumption and food waste could further increase the technical mitigation potential—however, economic and implementation considerations might limit the degree to which this technical potential could be realised in practice.