Relict high-Andean ecosystems challenge our concepts of naturalness and human impact

Abstract

What would current ecosystems be like without the impact of mankind? This question, which is critical for ecosystem management, has long remained unanswered due to a lack of present-day data from truly undisturbed ecosystems. Using mountaineering techniques, we accessed pristine relict ecosystems in the Peruvian Andes to provide this baseline data and compared it with the surrounding accessible and disturbed landscape. We show that natural ecosystems and human impact in the high Andes are radically different from preconceived ideas. Vegetation of these ‘lost worlds’ was dominated by plant species previously unknown to science that have become extinct in nearby human-affected ecosystems. Furthermore, natural vegetation had greater plant biomass with potentially as much as ten times more forest, but lower plant diversity. Contrary to our expectations, soils showed relatively little degradation when compared within a vegetation type, but differed mainly between forest and grassland ecosystems. At the landscape level, a presumed large-scale forest reduction resulted in a nowadays more acidic soilscape with higher carbon storage, partly ameliorating carbon loss through deforestation. Human impact in the high Andes, thus, had mixed effects on biodiversity, while soils and carbon stocks would have been mainly indirectly affected through a suggested large-scale vegetation change.

Elevational Shifts in the Topographic Position of Polylepis Forest Stands in the Andes of Southern Peru

“…The vegetation of the study area consists of alpine humid puna vegetation dominated by tussock grasses (Deyeuxia spp., Festuca spp.) and various shrub and herb species [22]. Forests of Polylepis racemosa R. & P. are found between 3800 m and 4200 m, and of P. subsericans J.F.…”

“…On the other hand, Polylepis forests have been observed to grow taller on eastern slopes because the increased solar radiation may increase overall temperatures [9]. There is also evidence for forests avoiding sites with topography-related water logging and/or cold-air ponding [20], and occurring preferentially at sites of inaccessible topography, where fires are not frequent [7,22]. Abiotic factors constraining Polylepis tree growth seem to vary between the species and geographical regions, with solar radiation being an important factor in humid and cloudy regions whereas water availability becomes more relevant in dry regions [9].…”

“…However, these highly impacted areas were excluded from this study, as we focused only on treeline-forming P. subsericans stands, which are mostly of difficult access. Nevertheless, even these sites have suffered from some degree of human impact, which has affected the naturalness of the current forest stand distribution [22].…”

“…This is particularly true for Polylepis forests and poses a challenge for detecting natural environmental preferences of the forests and for modelling forest distribution. The current forest locations can be biased towards sites that are the most inaccessible to humans, human-induced fires, and animal grazing, or they may have the highest capacity for recovery after human disturbance [2,7,22]. Both accessibility and recovery capacity are topography dependent, but only the latter is related to the ecology of the trees, whereas the former is more related to the ecology of humans and livestock.…”

Is Nigeria losing its natural vegetation and landscape? Assessing the landuse-landcover change trajectories and effects in Onitsha using remote sensing and GIS

“…Remarkable decline in the plant species was found in the study area during the study time. Several authors have recently reported high rates of plants species decline due to settlements and agricultural activities [66][67][68][69], which was intensified by population growth and rapid urbanization [70,71].…”