Globally, vineyards are expanding, and their management is intensifying, which poses concerns for their impact on biodiversity. What the past five decades have taught us is that agricultural expansion and intensification are bad news for biodiversity, by being the lead cause of habitat loss, contributing to species population declines and increasing extinctions worldwide (see Living Planet Report 2020). The question remains whether the impact of all crop production systems is equal and where vineyards stand in this.
Vineyards are widespread around the world, particularly across Mediterranean and tropical regions, which are climatically suitable for grape production. In these regions, vineyards have been a crucial part of the cultural and historical landscapes, being passed down through generations. Often in these cases, vineyards are managed with low chemical inputs, help to increase the heterogeneity (diversity and quality) of landscapes and contribute to supporting species-rich habitats. In other areas, vineyards are a recent addition, or undergoing rapid expansion, which threatens local habitats with loss and degradation. This poses questions over the ecological impact of vineyards, as many are increasingly more intensively managed. In many cases, these vineyards are important for the regional economy and livelihoods, making it even more important to understand how vineyards can be managed to support biodiversity conservation and to allow businesses to prosper.
In light of these changes, a team of scientists led by Anna Paiola, have been working to understand the impacts of viticulture on biodiversity and its interaction with management and the landscape. The researchers considered 218 research papers published since 1995 to understand how vineyards affect biodiversity conservation and summarised their findings in a paper published in 2020. Below I outline some key results from their work:
- How does increasing vineyard cover affect biodiversity?
The majority of studies found that increasing cover of vineyards in the landscape led to reduced biodiversity. This is likely due to decreased availability of suitable habitats for species, reduced quality of habitats or reduced connectivity between habitat patches. A reduction in habitat availability can occur when habitats such as woodlands are turned to vineyards, whilst habitat quality can be reduced when they shrink in size, or become polluted by vineyard management practices such as machine use (noise pollution) and chemical inputs. A reduction in connectivity can also occur when distances between remaining habitat patches increase, as parts of habitats are removed to allow space for vineyards. This was nicely illustrated by a study summarised by Paiola, which found that mammalian predators were more abundant in landscapes characterised by isolated and small vineyards with well-connected patches of natural habitats, which allowed continuity of movement.
In a small number of examples, increasing cover of vineyards helped to increase diversity, though this increase was limited to species thriving in open-habitats, such as grasslands, and farmland-specialists. For these species, vineyards can be a haven, especially if enriched with water bodies that attract invertebrates.
The structure of vineyards may be key to its effects on bird diversity. Vineyards were found to support less bird diversity than some other perennial crops, such as almond orchards and eucalyptus wood-plots, which was linked to the wire trellis system which makes vineyards very simple landscapes in comparison to woody crops. On the same lines, one study found that the trellis system affects vineyards’ suitability for birds. In this study, two trellis systems (see image below) were compared across Italian vineyards, and it was found that the traditional pergola trellis system supported more bird diversity, which the researchers put down to pergola vineyards being more complex and tree-like.
To help minimise the loss of diversity, vineyards can introduce certain landscape features that have a positive influence on bird species, and other species groups (see image above). For example, riparian corridors (“corridors” of natural habitat left untouched alongside rivers and streams) are fundamental for maintaining connectivity and aiding species’ movements. On similar lines, hedgerows and isolated trees can increase connectivity for birds, act as shelter and provide nest sites. All such features increase heterogeneity of vineyards and help to buffer against the negative effects of habitat loss that occurs during agricultural expansion.
- Is organic management better than conventional?
Perhaps surprisingly, the expected positive effect of organic farming on biodiversity was weak and inconsistent across different species groups. At the local scale (considering diversity at, or immediately around, vineyards), studies on birds and mammals are rare and yielded inconsistent results.
The positive effect of organic viticulture can be overshadowed by the impacts that conventional management has on biodiversity. Indeed, the authors found that organic and biodynamic viticulture weakly enhanced bird diversity at the landscape scale, though this effect disappeared in landscapes dominated by extensively managed vineyards. In landscapes that are a mixture of organic and non-organic vineyards, any positive effects of organic management can be cancelled out by the conventional activities, resulting in weak, mixed or zero net effects on biodiversity.
Similarities between organic and conventional vineyard management exist and impact biodiversity similarly. For example, both management styles use machinery, which has strong negative impact on bird diversity in vineyards. When it comes to other activities, such as chemical use, the difference in pesticide, fertiliser or fungicide use between organic and non-organic vineyards can be small, as some non-organic vineyards are low-input and manage their vineyards in-line with organic regimes.
Overall, the current research suggests not-so-optimistic effects of organic viticulture on biodiversity and disentangling the differing impacts of the two management styles on biodiversity requires further study. Nonetheless, it’s likely that the provision and maintenance of biodiversity-friendly natural habitat patches are crucial for enhancing the positive effects of organic viticulture on biodiversity.
- Cover crops support biodiversity and are an important management practice in vineyards
Over the recent years, the growing awareness of soil degradation and erosion has led many vineyards to try growing cover crops, with the benefits of this practice stretching to birds. Studies have found that ground-vegetated vineyards hosted more biodiversity than vineyards without ground cover. For birds, the effect of ground cover varied between different species, which can be largely explained by the differences in foraging habits. Granivorous birds (seed-eating) which forage on bare soil were unlikely to benefit from cover crops, but other species which eat insects from the ground, such as hoopoe, woodlark or common redstart, benefitted from the increased ground cover. These species prefer “kitchen-dining room” systems, where 40-60% of ground is left as bare soil and the rest is vegetated. This is because arthropods, which these birds feed on, are mostly abundant in taller grasses where visibility for birds is low so they rely on the bare soil patches to find and catch their prey. Additionally, some ground-breeding species, such as woodlark, require patches of dense vegetation cover for nesting, and likely benefit from cover crops. These results suggest that a mixed approach to ground-vegetation management that aims to increase the heterogeneity of sward heights is likely to have the highest positive impact on bird diversity.
The general patterns of the effects of vineyards on biodiversity mirror those observed in other crop systems, particularly when it comes to the importance of heterogeneity within vineyard-landscapes, and the mixed effects of organic management. This research review shed some light on the number of practices that vineyard managers can implement to support bird diversity on their land, and which practices to avoid, such as chemical weeding and tillage that have consistent negative effects for biodiversity across many crop systems.
Whilst providing answers to some questions, the review also found some missing pieces in the great agroecological puzzle of sustainable viticulture. A key missing piece is equal representation of world’s vineyard systems, as the majority of studies were carried out in North America and Europe, excluding the UK, which remains unstudied. Addressing this gap within the UK is a key aim of this research collaboration with the SWGB.
Linked paper: Paiola, A. et al. 2020. Exploring the potential of vineyards for biodiversity conservation and delivery of biodiversity-mediated ecosystem services: A global-scale systematic review. Science of the Total Environment, 706: https://doi.org/10.1016/j.scitotenv.2019.135839
About the author
My name’s Natalia Zielonka, and I’m a PhD candidate at the University of East Anglia. I’m supported by the UKRI BBSRC Norwich Research Park Biosciences Doctoral Training Partnership, and my great supervisors are Dr Lynn Dicks (based at the University of Cambridge) and Dr Simon Butler (UEA). If you have any questions then please don’t hesitate to contact me on [email protected] and via Twitter: @Nat_B_Zielonka.