Influence of Agropastoral System Components on Mountain Grassland Vulnerability Estimated by Connectivity Loss

Abstract

Over the last decades, global changes have altered the structure and properties of natural and semi-natural mountain grasslands. Those changes have contributed to grassland loss mainly through colonization by woody species at low elevations, and increases in biomass and greenness at high elevations. Nevertheless, the interactions between agropastoral components; i.e., ecological (grassland, environmental, and geolocation properties), social, and economic components, and their effects on the grasslands are still poorly understood. We estimated the vulnerability of dense grasslands in the Central Pyrenees, Spain, based on the connectivity loss (CL) among grassland patches that has occurred between the 1980s and the 2000s, as a result of i) an increase in biomass and greenness (CL-IBG), ii) woody encroachment (CL-WE), or iii) a decrease in biomass and greenness (CL-DBG). The environmental and grassland components of the agropastoral system were associated with the three processes, especially CL-IBG and CL-WE, in relation with the succession of vegetation toward climax communities, fostered by land abandonment and exacerbated by climate warming. CL-IBG occurred in pasture units that had a high proportion of dense grasslands and low current livestock pressure. CL-WE was most strongly associated with pasture units that had a high proportion of woody habitat and a large reduction in sheep and goat pressure between the 1930s and the 2000s. The economic component was correlated with the CL-WE and the CL-DBG; specifically, expensive pastures were the most productive and could maintain the highest rates of livestock grazing, which slowed down woody encroachment, but caused grassland degradation and DBG. In addition, CL-DBG was associated with geolocation of grasslands, mainly because livestock tend to graze closer to passable roads and buildings, where they cause grassland degradation. To properly manage the grasslands, an integrated management plan must be developed that includes an understanding of all components of the agropastoral system and takes into account all changes that have occurred in dense mountain grasslands. Addressing the problems individually risks the improvement of some grasslands and the deterioration of others.

Assessing Land Use-Cover Changes and Modelling Change Scenarios in Two Mountain Spanish National Parks

“…The main land use changes taking place in Ordesa NP are similar to the findings of other studies in the same area [34,36,90] and in other mountain systems on the planet [91,92]. From the point of view of landscape structure, the results are similar to those obtained by other authors [93] from two different approaches: fragmentation versus connectivity. We confirmed differences in the habitat fragmentation rates among, and within, PA networks [31].…”

Forests dynamics in the montane–alpine boundary: a comparative study using satellite imagery and climate data

“…Since the Middle Ages, the Pyrenees forest line has been artificially lowered to increase grassland availability for livestock summer pastures (Monserrat-Martí 1992). But since 1930, a marked reduction in agro-pastoral activities in mountain areas has taken place (Alados et al 2014, Gartzia et al 2016b, which has also affected the Ordesa and Monte Perdido National Park, where the grazing activity was maintained as part of the conservation programme (Gartzia et al 2016a). Consequently, we are facing important changes in the land cover in the national park, mainly below the 2100 m, where approximately 30% of shrubland has turned to forest and 12% of grasslands have become shrubland.…”

Assessment of prescribed fire and cutting as means of controlling the invasion of sub‐alpine grasslands by Echinospartum horridum

“…In the Central Pyrenees, traditional land use prevented woody species from invading grasslands (Montserrat & Fillat, ). In the second half of the 20 th century land abandonment led to woody invasion of those lands (Gartzia, Fillat, Pérez‐Cabello, & Alados, ; Lasanta‐Martinez et al., ). Between the 1980s and 2000s, a quarter of the sub‐alpine grasslands below 2100 m a.s.l were transformed into woody species habitat (Gartzia, Alados, & Perez‐Cabello, ).…”