Blog by Dr Tom Finch, Conservation Scientist, RSPB Centre for Conservation Science
Agriculture is a leading driver of biodiversity loss and environmental degradation. As a result, conservationists frequently find themselves promoting actions which either mitigate agriculture’s impacts on wildlife (often at the expense of food production) or exclude farming altogether. Because there is high (and often growing) demand for farm products, these actions risk displacing food production to other places, at the expense of distant habitats and species.
The land sharing / sparing model was conceived to address this problem by comparing regional conservation strategies which are equal in terms of overall food production.
Land sparing promotes large areas (>1 km2) of unfarmed natural habitat, with a reduced area of farmland compensated for by higher farmland yields per unit area. By contrast, land sharing involves lower-yielding, wildlife-friendly farming, with these lower yields compensated for by a larger area of farmland (and so less unfarmed natural habitat).
Previous studies comparing these two approaches (as well as intermediate ones) have mostly been conducted in tropical countries, and consistently show that most species of birds, butterflies, dung beetles and trees would experience larger populations under land sparing. However, the long history of agriculture in northern Europe (and the UK in particular) might lead to different results here. Additionally, in Europe we are interested in conserving quite a diverse community of species, including both natural habitat specialists and farmland species. These different groups are likely to do well under very different strategies – is there a compromise which can deliver for all?
Comparing sparing and sharing – The Fens and Salisbury Plain
Our research involved estimating the relationship between agricultural yield (production of human-edible calories per hectare, averaged across a 1-km square) and breeding densities of each of 110 bird species in two regions of southern England – the East Anglian Fens and Salisbury Plain in Wiltshire.
These ‘density-yield curves’ allow us to predict the breeding density of each species in nature reserves (wet grassland and fen in The Fens; chalk grassland and woodland in Salisbury Plain) as well as across the full observed gradient of agricultural yield. This allows us to predict the total regional population size of each species under scenarios which vary the area of nature reserves and the area and yield of farmland, always maintaining overall food production.
In The Fens, the mean relative population size of all species increases as the strategy shifts from sharing towards sparing, with natural habitat specialists (such as Bittern) benefitting from habitat restoration. However, farmland birds (such as Skylark) do poorly under land sparing so that, overall, the benefits of further habitat restoration towards extreme land sparing are counter-balanced by increasingly high agricultural yields; we see diminishing returns the closer we get to extreme land sparing.
In Salisbury Plain too, the average relative population size increases towards land sparing. Again, natural habitat specialists (such as Whinchat) benefit from habitat restoration. To some extent, farmland birds (like Corn Bunting) benefit from land sparing too, perhaps because they do well when some grassland is replaced by arable in mixed landscapes. When agricultural yields get too high though, these species decline towards extreme land sparing, counteracting the benefits to species such as Whinchat of continuing habitat restoration.
Photo: This graph shows the average response of bird populations (y-axis) across the sharing-sparing continuum. All scenarios compared produce the same amount of food overall. From left to right, the area of spared habitat (in km2) goes up, and so the yield of farmland must increase too. The black arrows show where we are today, approximately.
A compromise – sparing and sharing?
In summary, ‘intermediate’ land sparing (more spared land than at present, but with yield held somewhere below the maximum) does well in both regions (and extreme sparing does well in The Fens too), but there’s an inevitable conflict between strategies which are good for natural habitat specialists (Bittern, Whinchat) and those which are good for farmland birds (Skylark, Corn Bunting).
We therefore explored an alternative approach, in which some ‘spared’ land is managed not as natural habitat but as low-yielding wildlife-friendly farmland, with high-yield farming delivering the bulk of food production. This turned out to perform better than any other strategy in The Fens, and about as well as the best intermediate land sparing strategy in Salisbury Plain.
We call this scenario ‘three compartment sparing’, because it includes three land management compartments: (I) high-yield farming, which spares land elsewhere for (II) natural habitat and (III) low-yield farmland. This scenario therefore maintains overall food production whilst providing habitat for different types of species. Arguably, it’s a mix of both sparing (i.e. high-yield farmland spares land for other uses) and sharing (i.e. some wildlife-friendly farmland shares the function of conservation and a bit of food production).
What we’re not saying…
First, we’re not suggesting that high-yield farming will automatically spare land for nature conservation. This is unlikely to occur in the real world without strong policies to link one to the other. These policies might involve instruments to stimulate sustainable yield growth (such as subsidies and advice services) alongside the zoning of land for conservation.
Second, we’re not suggesting that unsustainable high-yield agricultural practices should continue on their current trajectory. Instead, we must identify and develop sustainable practices which can guarantee resilient, high-yield production in the long-term whilst minimising the degradation of natural capital such as soil and freshwater.
Finally, we’re not suggesting that high-yield farmland should be totally devoid of wildlife. Just as some high-yield practices will be unacceptable (see previous paragraph), some well-designed & well-implemented wildlife-friendly practices will be worth promoting even within specialised, high-yield farmland. Where these wildlife-friendly interventions incur a yield-penalty, their efficacy should be carefully considered, but in some cases they can be almost cost-free. For example, unproductive features such as buffer strips (designed to protect watercourses) are likely to deliver biodiversity co-benefits, whilst other wildlife-friendly actions might maintain (or even benefit) yields by promoting services such as pollination or natural pest control.
A continuing role for environmental land management schemes
The key finding of our research is simply that many bird species either avoid farmland altogether, or require such ‘intensive care’ within farmed landscapes that we can’t hope to have them everywhere without seriously compromising food production.
For nature to thrive then, we need more areas managed primarily for conservation – either as unfarmed nature reserves or through low-yield, wildlife-friendly farmland. To maximise the area of conservation land whilst still delivering food for people, we’ll also need large areas of specialised, high-yielding, but sustainably managed farmland, where nature conservation takes more of a back seat.
All three of these ‘compartments’ could be supported by agri-environment-like schemes which are, for example, the primary means of funding the restoration and management of natural and semi-natural habitats in the UK. These schemes also support the types of management needed in the low-yielding, wildlife-friendly compartment (e.g. organic conversion and maintenance payments, or The Cirl Bunting Project). Even on specialised high-yield farmland, agri-environment schemes can help deliver sustainability & resilience, in addition to ‘low-cost’ conservation measures.
So, in the context of government efforts to design new, post-Brexit policies to replace Europe’s Common Agricultural Policy, joined-up land management schemes across all three ‘compartments’ could have a major role to play.
Trade-offs
Evaluating land-use strategies through the lens of land sparing and sharing helps us to be clear-minded about the trade-offs between nature conservation and food production. In many respects, using this model to find the optimum balance between the three compartments is about getting as close as we can to a ‘cake and eat it’ solution, whilst recognising that we can’t have everything, everywhere.
As well as considering the balance between food production and bird conservation, we’re currently working on developing this model to consider additional environmental outcomes including butterfly conservation, greenhouse gas emissions, nature-based recreation and diffuse pollution.
Whilst this approach can help to inform policies such as spatial targeting for post-Brexit land management schemes, it’s not a silver bullet. To make it operable in the UK would require a degree of rural land-use planning that would challenge the status quo. We must also be clear about which sorts of high-yield agricultural practices are environmentally acceptable, whilst acknowledging the environmental costs of lower-yielding practices in terms of overall land footprint. If we recognise these important caveats, then the sparing-sharing model can play an important role in setting out a strategy for future land-use that balances the needs of food production and the natural environment.
Finch, Gillings, Green, Massimino, Peach & Balmford (2019) Bird conservation and the land sharing-sparing continuum in farmland-dominated landscapes of lowland England. Conservation Biology. DOI: 10.1111/cobi.13316
Shows we need more land spared as well as the current agri-environment partly-shared land. We need less consumption and fewer people on the planet at one time too.