Establishing herbivory baselines: A new perspective on methane emissions in Spanish open ecosystems

Recent findings published in Landscape Ecology reveal that a considerable amount of methane emissions caused by herbivores—traditionally linked to modern livestock—could originate from natural ecosystem processes. This discovery calls for reevaluating the environmental impact of wild and domesticated herbivores.

Past discourse on livestock systems largely assumed that historic wild herbivore populations were much smaller than today’s livestock numbers, causing the methane contributions of wild herbivores to be overlooked in ecological evaluations. As a result, all herbivore-related environmental impacts were attributed to domestic herbivores, categorized as a byproduct of human activity.

Challenging this conventional view, BC3’s research team led by Rubén Serrano-Zulueta spearheads research that sets out to establish baseline figures for herbivore populations within Spain’s open ecosystems. By analyzing data from 11 protected areas in Spain, this study reveals that present herbivore populations fall well below these new baselines, indicating a historical underestimation of methane emissions from wild herbivores.

“Our analysis indicates that approximately 23% of what we consider emissions from extensive livestock grazing in Spanish open ecosystems coincide with the natural baseline of these ecosystems,” Serrano-Zulueta elaborates. “This means that, at the very least, one eighth of the emissions charged to animal production could be part of the ecosystem’s innate emissions, accounting for around 13% of the livestock methane reported in Spain’s national greenhouse gas inventories.”

The study identifies two primary reasons for the current decline in herbivore populations relative to historical baselines: the loss of native grazing species, and altered migratory patterns. “Spain’s traditional farming practices have significantly reshaped its landscapes, replacing the indigenous grazing species with domesticated herds, to the point where some native grazers are extinct,” explains Pablo Manzano, Ikerbasque researcher at BC3. “Moreover, with the rise of land abandonment, there’s a notable increase in browser species, potentially tipping the ecosystems out of balance. Therefore, we propose strategically integrating domestic grazing animals to maintain the ecological roles that can’t be fulfilled by the extant wild, mostly browser, ungulates.”

Forming the first segment of Rubén Serrano-Zulueta’s doctoral thesis, this research recontextualizes the debate on methane emissions from livestock. It underscores the value of Spanish open ecosystems as viable climatic landscapes alongside natural forests. Supported by the Basque Government’s Ikertalent Program, the Deputy Ministry of Agriculture, Fisheries, and Food Policy, and further aided by the Candido Iturriaga and Maria Dañobeitia Foundation, the study marks a significant advance in comprehending the influence of herbivores on ecosystem functioning and their climatic effects.

For a detailed exploration of the research findings, you can access the full paper here.

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María de Maeztu Excellence Unit 2023-2027 Ref. CEX2021-001201-M, funded by MCIN/AEI /10.13039/501100011033

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