The social and ecological value of transhumance and extensive pastoralism against global change
Pastoral ecosystems have a great ecological value despite having been considered, for most of the last century, less desirable ecological states than forest ecosystems. The predominance of linear models of ecological succession, which propose deterministic and predictable climax states, had a massive influence in different academic fields and on land management, and this influence is still very evident in the biases of society towards «forested» ecosystems. However, we have now solid evidence which clearly points out that Pleistocene landscapes were much more complex, with important areas of open habitat where herbivores played a critical role. This interpretation would also be more compatible with modern models of alternative stable states, which generate much more scientific consensus than linear succession models.
The expansion of forest environments might be problematic, as this implies an important loss of biodiversity, especially of those species which are intolerant to shade, or which depend on open spaces, as well as the increased role of fires as the main factor regulating biomass in ecosystems. On the other hand, landscapes with adequate herbivory regimes are more heterogeneous, have more diversity of species, show more mechanisms for seed distribution, are more connected due to the movement of herds, improve nutrient recycling in soils, regulate biomass and the albedo effect, allow for the survival or carrion-eaters and other species that depend on the presence of ungulates, and, ultimately, represent much more resilient ecological states than continuous forests. Contrary to what is often held to be true, methane emission by ruminants do not play a relevant role in the increase of greenhouse gases in the atmosphere, the basic cause being the burning of fossil fuels. The emissions from domestic herbivores raised extensively form part of the natural carbon cycle, and would be similar to those produced if these animals were not present in the system, although they would be channelled through other organisms. Moreover, pastoral ecosystems concentrate carbon sequestration inside the soil, a safer reservoir than aerial biomass, which is more prone to rapid oxidisation through fires or decomposers.
Certain cultural landscapes with presence of domestic herbivores, which are common since Neolithic times, might represent, in fact, more desirable ecological states than continuous forest. In this sense, the livestock management practices that benefit biodiversity, are more sustainable and are more adapted to seasonality and climate tensions, are those which involve nomadic movement and transhumance. Transhumance is a traditional livestock management practice consisting in the seasonal movement of livestock between upper areas (or higher latitudes) dedicated to summer pastures, and lower regions (or lower latitudes) where livestock spends the winter. These seasonal livestock movements follow regular, established routes.
In Spain, livestock drove roads (commonly called «cañadas») are the traditional routes used by livestock herds for their seasonal movements in search of more productive pastures. Drove roads have important ecological effects at different spatial scales. Thanks to traditional pastoralism and the protection of pastures from ploughing over centuries, livestock drove roads combine pastureland with clumps of woody vegetation, hedges and other types of vegetation linked to ancient structures such as stone walls. At the landscape level, drove roads significantly increase habitat heterogeneity, with marked edge effects, to such an extent that in agricultural and forest matrices they act as biodiversity «hotspots». On a wider scale, transhumant livestock disperse seeds along several hundred kilometres, playing an important role in connecting plant populations, and ensuring the preservation of local species. Likewise, livestock drove roads have also proved their important role in maintaining several ecosystem functions and services, such as connectivity, soil fertility, erosion control, pollination, and different cultural services.
The ecological role of drove roads is closely linked to the preservation of livestock movements. Unfortunately, the progressive abandonment of transhumance has favoured the invasion of drove roads by crops, human-built infrastructure, and other aggressive uses such as motor sports. These drivers are threatening the important role of livestock drove roads as ecological corridors: landscape fragmentation and isolation of the Red Natura 2000 sites due to the development of intensive agriculture, urban expansion and grey infrastructure like roads and railways, has been recognised as an important problem for conservation in Europe.
In this context, reconnecting Natura 2000 sites via green infrastructure has been proposed as a critical conservation issue. Restoration of the abandoned livestock drove roads and protection of those still in use can be an excellent strategy to promote green infrastructure in the territory. Spain is a particularly favourable case for this, due to its extensive network of livestock drove roads (approximately 125,000 km which cover 421,000 ha, almost 1% of the country’s surface area) which is legally protected since 1995 under the Ley de Vías Pecuarias 3/1995 (Drove Roads’ Act). Moreover, Spain is undergoing intense phenomena of land use change and habitat fragmentation, which makes the implementation of green infrastructure critical for the functional integration of landscape fragments and, on a larger scale, for reconnecting well-preserved natural areas, such as protected Natura 2000 sites.
To address this challenge, we launched the LIFE CAÑADAS project in 2019, aiming to improve the role of the Spanish network of drove roads as green infrastructure that provides connectivity among Natura 2000 sites, by improving their conservation status and the ecosystem services they supply, and by restoring their multi-functionality and ensuring their appropriate and sustainable management.
Violeta Hevia, Francisco M. Azcárate and José A. González are researchers in the LIFE CAÑADAS project of the Departamento de Ecología (Ecology Department) at the Universidad Autónoma de Madrid (UAM, Madrid, Spain). The three authors participated in the session of December 21, 2022 of the conference Shepherds, livestock and landscapes: Ancestral solutions to recover the future, organized throughout the month of December by the Association for the Study of Human Ecology, the Office of Sustainability of the UAM and the Faculty of Sciences of the UAM. The materials from this activity are available at IX Scientific Seminar of the ASHE.
The photo which illustrates this monthly exhibit was taken by Alberto Saiz, and was taken during the transhumance organised in Spring 2021 in the Comunidad de Madrid by the LIFE CAÑADAS project, together with the Asociación Trashumancia y Naturaleza (Transhumance and Nature Association) and Raúl Serrano.