Carbon footprint of transhumant sheep farms: accounting for natural baseline emissions in Mediterranean systems

Abstract

Purpose Transhumance has rarely been analyzed through LCA approaches, and there is little evidence about its emissions level when conducted under different practices (by truck or on foot) or compared to sedentary livestock systems. Moreover, mobile pastoralism is strongly linked to natural resources by its seasonal grazing patterns, thereby occupying the niche of wild herbivores. Considering natural emission baselines in these ecosystems could have relevant effects when estimating their carbon footprint. Materials and methods Inventory data of 20 sheep farms was collected to estimate the carbon footprint (CF) of lamb meat produced. Farms were divided into three sub-groups representing typical management practices in the region: (1) sedentary (SED), (2) transhumance by truck (THT), and (3) transhumance on foot (THF). Livestock GHG emissions were modeled according to herd structure and IPCC guidelines. Off-farm emissions from external feeds and fuels were accounted based on existent LCA databases. A natural baseline of wild herbivores was established from the population of red deer reported in a hunting preserve, previously considered to be a reference for the natural carrying capacity in Mediterranean ecosystems. GHG emissions of wild herbivores were estimated through two methods based on (1) IPCC guidelines and (2) allometric regression equations. Results and discussion Carbon footprint ranged from 16.5 up to 26.9 kgCO2-eq/kg of lamb liveweight (LW). Significant differences were identified among sedentary and transhumant farms, the latter consistently showing lower CF values (SED: 25.1 kg CO2-eq/kg LW, THT: 18.3 kg CO2-eq/kg LW, THF: 18.2 kg CO2-eq/kg LW). Sedentary farms resulted in higher GHG emissions (+ 27%) and higher CO2 and N2O, contributions derived from the consumption of additional feeds. Both methods applied to compute emissions for wild herbivores led to similar results (25.3–26.8 Mg CO2-eq/km2), comparatively lower than estimation for transhumant sheep (47.7 Mg CO2-eq/km2). When considering natural baseline emissions, the CF of transhumant lamb meat is reduced by almost 30%, reaching values quite below those reported for intensive lamb production systems in Spain. Conclusions From our results, mobility of grazing livestock can be considered as a strategy promoting climate change mitigation. This is achieved mainly by reducing the need of external feeds, while maximizing the use of local forage resources that otherwise would be difficult to valorize. Further reductions in the CF result when considering natural baseline emissions. The application of this new GHG accounting perspective could have relevant implications when aiming at climate neutrality of grazing-based ruminant systems.

A Comparative Analysis of Carbon Footprint in the Andalusian Autochthonous Dairy Goat Production Systems

“…Designing compensation regimes for the ecosystem services provided by pastoral systems could be a tool to improve the competitiveness of these systems [ 46 ], which are otherwise at a disadvantage compared to permanently establishing intensive systems, both from an economic and productive point of view [ 47 ]. Areas with low cropping potential (e.g., arid or mountainous areas), such as the farms studied, depend on grazing [ 14 , 17 ]. While vegetation plays a critical role in mitigating climate change, it also plays an important role in supporting global biodiversity and providing many goods and services to humans [ 9 , 48 ].…”

“…On the other hand, soil health and fertility and carbon sink ability by both soil and vegetation can be favored by properly managed ruminant grazing. In this sense, pasture-based carbon sequestration can mitigate, to varying degrees, the GHG emitted by the livestock it feeds as well [ 13 , 14 ]. Previous studies have shown that taking carbon sinks into account in the net GHG emission balance significantly reduces emissions per unit of product on farms with land-based grazing [ 6 , 8 , 15 ].…”

Herbivory baseline estimates in Spanish Protected Areas, and environmental implications.

“…An herbivory baseline that enteric herbivore emissions have been part of the natural uxes in the past and have a of inevitability future, because such emissions are consubstantial to the grazing ecological niche that dominates Open Ecosystems (Manzano and White 2019). Considering a signi cant fraction of herbivory as a natural process, as done in the present study, or in Pardo et al (2023) contrasts from the conventional approach of most studies. All livestock herbivory is usually considered as purely anthropic, and so are all enteric caused (e.g.…”

“…But domestic grazing herbivores can indeed ful l ecological roles that are equivalent to wild herbivores, and their densities can also be equivalent (Manzano et al 2023a). At the same time, some authors have demanded that the consideration of baselines can be important in environmental assessment (Pardo et al 2023) and policymaking (Moncrieff et al 2016), for example, when supporting or limiting pastoralism (Manzano et al 2023a). In sum, new methodological approaches demand delving into a speci c framework for Open Ecosystems that explicitly includes and quanti es baseline values (Manzano and White 2019).…”

Comparable GHG emissions from animals in wildlife and livestock-dominated savannas

“…We can help nuancing current calls to shift into plant-based diets to increase the sustainability of the food system 24 , because the resulting abandoned land will clearly not be a zero-emission scenario 8 . Instead, livestock systems that mimic natural migratory herbivore systems as much as possible, such as mobile pastoralism, should be promoted to mitigate climate change at the expense of industrialized high-input production systems 10,25 . In addition, decisions to promote wildlife conservation or pastoralism cannot rest by putative advantages to GHG emissions but must focus on other reasons or effects.…”