Potential Responses of Vascular Plants from the Pristine “Lost World” of the Neotropical Guayana Highlands to Global Warming: Review and New Perspectives

The neotropical Guayana Highlands (GH) are one of the few remaining pristine environments on Earth, and they host amazing biodiversity with a high degree endemism, especially among vascular plants. Despite the lack of direct human disturbance, GH plants and their communities are threatened with extinction from habitat loss due to global warming (GW). Geographic information systems simulations involving the entire known vascular GH flora (>2430 species) predict potential GW-driven extinctions on the order of 80% by the end of this century, including nearly half of the endemic species. These estimates and the assessment of an environmental impact value for each species led to the hierarchization of plants by their risk of habitat loss and the definition of priority conservation categories. However, the predictions assume that all species will respond to GW by migrating upward and at equal rates, which is unlikely, so current estimates should be considered preliminary and incomplete (although they represent the best that can be done with the existing information). Other potential environmental forcings (i.e., precipitation shifts, an increase in the atmospheric CO2 concentration) and idiosyncratic plant responses (i.e., resistance, phenotypic acclimation, rapid evolution) should also be considered, so detailed eco-physiological studies of the more threatened species are urgently needed. The main obstacles to developing such studies are the remoteness and inaccessibility of the GH and, especially, the difficulty in obtaining official permits for fieldwork. © 2017, Frontiers Research Foundation. All rights reserved.Peer reviewe

Undervalued impacts of sea-level rise: vanishing deltas

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A spatiotemporal gradient in the anthropization of Pyrenean landscape. Preliminary report

A preliminary analysis of the timing of landscape anthropization in the southern-central Pyrenees shows the occurrence of an elevational gradient from the Bronze Age (basal belts) to the Middle Ages (alpine belts). This relationship is statistically significant and suggests an average anthropization rate of 40 m in elevation per century. The elevational gradient is most clear between the Bronze Age and the Roman occupation, suggesting a progressive upward anthropization trend from the south with the likely involvement of Iberian cultures. During the Middle Ages, a massive anthropization pattern of subalpine/alpine areas is observed; this pattern is chronologically consistent with the incursion of northern cultures crossing the Pyrenees and the development of extensive high-mountain pastoralism and horizontal transhumance. In general, the progression of upward anthropization has occurred during warm climatic phases. Further work is needed to confirm these observations, especially in areas with few available paleoecological studies, notably the basal and montane belts. It could be interesting to develop similar studies of other Pyrenean regions and other mountain ranges

The neotropical Gran Sabana region: Palaeoecology and conservation

The Gran Sabana (GS) is a key region for understanding the origin of neotropical savannas and is an ideal location to test ecological hypotheses on long-term vegetation dynamics under the action of natural and anthropogenic drivers. The conservation of the GS is a controversial issue because of the confluence of disparate cultural and socio-economic interests, with a strong debate surrounding fire practices by indigenous people. Late glacial to Holocene pollen and charcoal records obtained thus far in this region have documented the main palaeoecological trends along with the climatic and anthropogenic (mostly fire) drivers involved. Here, we discuss how these records can be used to inform conservation and restoration practices in the GS. The main points of the discussion are the local versus regional character of palaeoecological evidence, the support provided by this evidence for the existing fire management proposals and the role of spatiotemporal environmental and ecological heterogeneity in the definition and evaluation of realistic restoration targets. A general conclusion is that past ecological reconstructions do not fully support either of the current options for fire management, that is, either total fire suppression or the continuity of indigenous fire practices. It is recommended to replace this dual and rigid conservation framework with a more diverse and flexible approach that considers the complex spatiotemporal heterogeneity documented in palaeoecological records. © The Author(s) 2016.This research was funded by the Ministry of Education and Science (grant CGL2006-00974/BOS), the Ministry of Science and Innovation (grant CGL2009-07069/BOS) and the Banco de Bilbao Vizcaya Argentaria Foundation (grants BIOCON 2004-90/05 and BIOCON 2008-031).Peer reviewe

Potential Responses of Vascular Plants from the Pristine 'Lost World' of the Neotropical Guayana Highlands to Global Warming: Review and New Perspectives

The neotropical Guayana Highlands (GH) are one of the few remaining pristine environments on Earth, and they host amazing biodiversity with a high degree endemism, especially among vascular plants. Despite the lack of direct human disturbance, GH plants and their communities are threatened with extinction from habitat loss due to global warming (GW). Geographic information systems simulations involving the entire known vascular GH flora (>2430 species) predict potential GW-driven extinctions on the order of 80% by the end of this century, including nearly half of the endemic species. These estimates and the assessment of an environmental impact value for each species led to the hierarchization of plants by their risk of habitat loss and the definition of priority conservation categories. However, the predictions assume that all species will respond to GW by migrating upward and at equal rates, which is unlikely, so current estimates should be considered preliminary and incomplete (although they represent the best that can be done with the existing information). Other potential environmental forcings (i.e., precipitation shifts, an increase in the atmospheric CO2 concentration) and idiosyncratic plant responses (i.e., resistance, phenotypic acclimation, rapid evolution) should also be considered, so detailed eco-physiological studies of the more threatened species are urgently needed. The main obstacles to developing such studies are the remoteness and inaccessibility of the GH and, especially, the difficulty in obtaining official permits for fieldwork

The neotropical Gran Sabana region: palaeoecology and conservation

The Gran Sabana (GS) is a key region for understanding the origin of neotropical savannas and is an ideal location to test ecological hypotheses on long-term vegetation dynamics under the action of natural and anthropogenic drivers. The conservation of the GS is a controversial issue because of the confluence of disparate cultural and socio-economic interests, with a strong debate surrounding fire practices by indigenous people. Late glacial to Holocene pollen and charcoal records obtained thus far in this region have documented the main palaeoecological trends along with the climatic and anthropogenic (mostly fire) drivers involved. Here we discuss how these records can be used to inform conservation and restoration practices in the GS. The main points of the discussion are the local vs. regional character of palaeoecological evidence, the support provided by this evidence for the existing fire management proposals and the role of spatiotemporal environmental and ecological heterogeneity in the definition and evaluation of realistic restoration targets. A general conclusion is that past ecological reconstructions do not fully support either of the current options for fire management, i.e., either total fire suppression or the continuity of indigenous fire practices. It is recommended to replace this dual and rigid conservation framework with a more diverse and flexible approach that considers the complex spatiotemporal heterogeneity documented in palaeoecological records

Present climate of lake Montcortès (Central Pyrenees): paleoclimatic relevance and insights on future warming

The varved sediments of the Pyrenean Lake Montcortès (Pallars Sobirà, Lleida) embody a unique continuous high-resolution (annual) paleoarchive of the last 3000 years for the circum-Mediterranean region. A variety of paleoclimatic and paleoecological records have been retrieved from these uncommon sediments that have turned the lake into a regional reference. Present-day geographical, geological, ecological and limnological features of the lake and its surroundings are reasonably well known but the lack of a local weather station has prevented characterization of current climate, which is important to develop modern-analog studies for paleoclimatic reconstruction and to forecast the potential impacts of future global warming. Here, the local climate of the Montcortès area for the period 1955-2020 is characterized using a network of nearby stations situated along an elevational transect in the same river basin of the lake. The finding of statistically significant elevational gradients for average temperature and precipitation (-0.59 °C and 82 mm per 100 m elevation, respectively) has enabled to estimate these parameters and their seasonal regime for the lake site. The estimated average annual temperature is 9.7±0.8 °C and the estimated total annual precipitation is 1031±34 mm, in average. A representative climograph has been shaped with these data that can serve as a synthetic descriptive and comparative climatic tool. The same analysis has provided climatic data for modern-analog studies useful to improve the interpretation of sedimentary records in climatic and ecological terms. In addition, the seasonal slope shifting of the climatic elevational gradients has been useful to gain insights about possible future climatic trends under a warming scenari

Neotropical vegetation responses to Younger Dryas climates as analogs for future climate change scenarios and lessons for conservation.

The Younger Dryas (YD) climatic reversal (12.86-11.65 cal ky BP), especially the warming initiated at ∼12.6 cal ky BP, and the associated vegetation changes have been proposed as past analogs to forecast the potential vegetation responses to future global warming. In this paper, we applied this model to highland and midland Neotropical localities. We used pollen analysis of lake sediments to record vegetation responses to YD climatic changes, which are reconstructed from independent paleoclimatic proxies such as the Mg/Ca ratio on foraminiferal tests and Equilibrium Line Altitude (ELA) for paleotemperature, and grayscale density and Titanium content for paleoprecipitation. Paleoclimatic reconstructions at both highlands and midlands showed a clear YD signal with a conspicuous warming extending into the early Holocene. A small percentage of taxa resulted to be sensitive to these YD climate changes. Response lags were negligible at the resolution of the study. However, changes in the sensitive taxa were relevant enough to determine changes in biodiversity and taxonomic composition. Highland vegetation experienced mainly intra-community reorganizations, whereas midland vegetation underwent major changes leading to community substitutions. This was explained in terms of threshold-crossing non-linear responses in which the coupling of climatic and other forcings (fire) was proposed as the main driving mechanism. Paleoecology provides meaningful insights on the responses of highland and midland Neotropical vegetation to the YD climatic reversal. Biotic responses at both individual (species) and collective (assemblage) levels showed patterns and processes of vegetation change useful to understand its ecological dynamics, as well as the mechanisms and external drivers involved. The use of paleoecological methods to document the biotic responses to the YD climate shifts can be useful to help forecasting the potential consequences of future global warming. Due to its quasi-global character, the YD reversal emerges as a well suited candidate for providing useful insights of global scope by analyzing the corresponding biotic responses virtually at any geographical and biological setting

Undervalued impacts of sea-level rise: vanishing deltas

Current SLR might be considered a significant extinction force because of its high potential to degrade, reduce, or eliminate deltaic and coastal habitats, thereby promoting huge diversity losses. Nonetheless, the effects of SLR are still too frequently ignored in terms of designing biodiversity conservation strategies or developing urban/rural areas. SLR represents a serious threat to millions of people living in densely populated deltas. Almost 40% of major deltas, most of them already overpopulated, may increase their population density by >100 hab./km2 (2000-2050). Most adaptive measures to confront SLR in deltaic habitats will become more expensive and more difficult to execute with continued human growth. Growing populations also increasingly exploit biodiversity goods and services, adding stress to the deltaic ecosystems that strive to acclimatize to SLR. Beyond a certain point, additional pressure would favor their collapse. To achieve some degree of success, adaptive measures might be reinforced by specific policies and regulations, such as migration control and development restrictions. Biodiverse and sparsely populated deltas housing ethnic minorities may remain unattended and rely on their own resilience to SLR, whereas wealthy and densely populated deltas will be given priority. The selection of strategies to adequately address SLR in delta environments should be performed in the context of long-term planning. Because the long term is full of uncertainties, space- and time-specific research efforts should be devoted to address knowledge gaps before information demands become progressively too pressing

Late Holocene vegetation and fire dynamics on the summits of the Guayana Highlands: The Uei-tepui palynological record

The summits of the tepuis (sandstone table mountains of the Neotropical Guayana region-Guayana Highlands, GH) have been considered valuable for palaeoecological studies due to their pristine nature, which emphasizes the role of natural (i.e. non-human) factors on ecological change. Anthropogenic fires, very frequent in the surrounding Gran Sabana (GS) uplands, have very rarely been documented in the GH, and are therefore not considered an important ecological factor in the high-tepui biome. This paper reports the palynological and charcoal results of a Late Holocene sequence from the summit of Uei-tepui (2104 m elevation), where extensive signs of fire were recently observed. Since ~. 2000 cal yr BP, the landscape of the study site has been dominated by meadows with occasional shrubs and cloud forests, which underwent expansions and contractions driven by climate changes and fire. A major vegetation shift occurred in the mid-18th century, when a sustained increase in local fires favoured the expansion of the low and spreading Cyrilla racemiflora shrublands at the expense of meadows and forests. Uei-tepui fires most probably were the result of human activities and reached the summit under study from the GS uplands through the vegetated slopes that characterize this tepui. The mostly anthropogenic nature of these fires, especially the more recent ones, is supported by the initial occurrence of wetter conditions, and by its coincidence with significant social changes in the GS indigenous populations, mainly the European contact. The emergence of fire as a disturbing agent of the GH biome highlights the need for an effective management plan in the GS uplands, where the vast majority of present-day fires originate, and designed in collaboration with the indigenous communities. Proactive conservation measures are considered even more important under future warming projections in the area. © 2016 Elsevier B.V.This research was supported by projects BIOCON 2004 90/05, BIOCON 08-188/09 (BBVA Foundation, Spain), CGL2006-00974/BOS (Ministry of Education and Science, Spain) and CGL2009-07069/BOS (Ministry of Science and Innovation, Spain) to V. Rull, and a predoctoral grant to E. Safont from the University of Barcelona. Fieldwork permits were provided by the Ministry of Science and Technology of Venezuela (no. 0000013, 5 Jan. 2007) and the Ministry of Environment of the same country (no. IE-085, 9 Feb. 2007).Peer reviewe