Books by William Gosling
This updated and expanded second edition of a much lauded work provides a current overview of the... more This updated and expanded second edition of a much lauded work provides a current overview of the impacts of climate change on tropical forests. The authors also investigate past, present and future climatic influences on the ecosystems with the highest biodiversity on the planet. Tropical Rainforest Responses to Climatic Change, Second Edition, looks at how tropical rain forest ecology is altered by climate change, rather than simply seeing how plant communities were altered. Shifting the emphasis on to ecological processes, e.g. how diversity is structured by climate and the subsequent impact on tropical forest ecology, provides the reader with a more comprehensive coverage. A major theme of the book is the interaction between humans, climate and forest ecology. The authors, all foremost experts in their fields, explore the long term occupation of tropical systems, the influence of fire and the future climatic effects of deforestation, together with anthropogenic emissions. Incorporating modelling of past and future systems paves the way for a discussion of conservation from a climatic perspective, rather than the usual plea to stop logging. This second edition provides an updated text in this rapidly evolving field. The existing chapters are revised and updated and two entirely new chapters deal with Central America and the effect of fire on wet forest systems. In the first new chapter, the paleoclimate and ecological record from Central America (Lozano, Correa, Bush) is discussed, while the other deals with the impact of fire on tropical ecosystems.
Drawing on the very latest research, this book explains what biodiversity is and explores its evo... more Drawing on the very latest research, this book explains what biodiversity is and explores its evolution, from 3.5 billion years ago to the present day. It discusses the importance of the world’s ecosystems and how directly or indirectly humans are responsible for the fate of nature.
Every single day we come face-to-face with nature’s remarkable diversity, but often don’t even realize it. From the plant and animal products that make up our breakfast to the ecosystems that help to produce clean water, our very survival depends upon the variety of plant and animal life on our planet.
Crucially, Fragile Web also examines what can be done to protect the natural world and why it matters. Although we cannot undo all that we have done, ignoring the current crisis for biodiversity could fundamentally change the lives of future generations.
Fully illustrated with colour photographs, diagrams and maps, this book is a timely snapshot of the state of life on Earth.
Papers by William Gosling
The Holocene, 2013
Human access to natural resources (or provisioning ecosystem services) is controlled by climate c... more Human access to natural resources (or provisioning ecosystem services) is controlled by climate conditions and usage. In the central Andean highlands, around Lake Titicaca, water and woodlands have been critical resources for human populations over the last 5000 years. During this time period human society developed of mobile hunter-forager groups into settled agrarian populations (c. 3400 years ago) through to the rise of some of the first ‘civilizations’ in the central Andes (c. 2500 years ago). Records of past environmental and vegetation change reveal that coincident with these societal reorganizations were variations in the availability of water and woodland resource. Prior to Hispanic arrival in the central Andes (before A.D. 1532) changes in availability of natural resources are shown to be concomitant with societal reorganizations; however, changes in societal organisation are shown not to necessarily result in the degradation of ecosystem services (i.e. woodland resource available). Through the last 5000 years three concomitant repeated adaptive cycles of destabilization, reorganisation, growth and maxima are identified in human and ecological systems. This suggests that long-term (>100 year) societal development was paced by both increases and decreases in ecosystem service provision. The approach of past societies to dealing with changes in baseline resource availability may provide a useful model for policy makers to consider in the light of the predicted scarcity of resource over the coming decades.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2013
Recent investigations of wetlands in western Amazonia have revealed the presence of extensive pe... more Recent investigations of wetlands in western Amazonia have revealed the presence of extensive peat deposits up to 7.5 m thick developing under a variety of vegetation types. We report the first attempt to establish the long-term (centennial to millennial scale) vegetation history of one of these peatland sites, Quistococha, a palm swamp close to Iquitos in northern Peru. Pollen and sedimentological analyses show that peat formation began at the core site under sedge fen or floating mat vegetation c. 2200 calendar years before present (cal yr BP). A seasonally flooded woodland developed c. 1880 cal yr BP. The permanently waterlogged palm swamp which persists today began to form c. 1000 cal yr BP, with the present vegetation community established by c. 400 years ago. The vegetation at this site has undergone continuous change throughout the period of peat formation, with several abrupt transitions, and reversals and repetitions in the apparent trajectory of change. The pollen data, combined with sedimentary evidence, suggest that the dominant control on ecosystem functioning and development is the flooding regime. There appears to have been a decrease in fluvial influence over time. There is no clear evidence of direct climatic or anthropogenic influence although we cannot rule out the possibility of climatically driven hydrological changes. Our results caution against adopting a simple model of peatland vegetation succession in this region.
The last glacial period was marked by multiple, abrupt reorganizations of ocean and atmosphere ci... more The last glacial period was marked by multiple, abrupt reorganizations of ocean and atmosphere circulation1. On thousand-year timescales, slowing of the Atlantic meridional overturning circulation was associated with cooling in the high northern latitudes, whereas strengthened circulation was linked to northern warming1,2. In the tropics, these millennial-scale events were primarily reflected in altered patterns of precipitation3. These hydrologic fluctuations induced ecological changes in the Atlantic seaboard and the high Andes2, but less is known about the Amazon Basin. Here we reconstruct precipitation over Amazonian Ecuador over the past 94,000 years using a δ18O record from speleothems collected in Santiago Cave in western Amazonia. We interpret the variability of the δ18O record as changes in the source and amount of precipitation. With the exception of the period between 40,000 and 17,000 years ago, abrupt, high-frequency changes coincide with shifts in North Atlantic circulation, indicating a high-latitude influence on Amazonian precipitation over millennial timescales. On longer timescales, the record shows a relationship to precessional changes in the Earth’s orbit. In light of the lack of extreme aridity in our records, we conclude that ecosystems in western Amazonia have not experienced prolonged drying over the past 94,000 years.
We present the first palaeolimnological investigation of chironomid larval assemblages from the B... more We present the first palaeolimnological investigation of chironomid larval assemblages from the Bolivian Eastern Cordillera. Taxonomic diagnoses are provided for the 10 chironomid taxa (subfamilies: Chironominae, Orthocladiinae and Tanypodinae) identified in the lake sediments. We compared changes in the chironomid assemblage from two Andean sites with previously reported palynological, charcoal and geochemical data, and highlight the potential of chironomid analysis to provide additional insights into environmental change in this region of high biodiversity over the last 18,000 years. At Lake Challacaba (17°33.257’ S, 65°34.024’W; 3,400 m asl), the chironomid and geochemical data indicate periodic desiccation and hypersalinty of the basin c. 4,000–3,460 cal yr BP. Increased abundance of Chironomus sp. at c. 1,000 cal yr BP suggests a change in human activity, supporting inferences from the pollen and spore records, which indicate elevated pastoral agriculture at this time. The greatest assemblage change in the chironomid record from Laguna Khomer Kocha Upper (17°16.514’ S, 65°43.945’W; 4153 m asl) occurred at c. 6,380 cal yr BP, concomitant with an increase in marsh woodland taxa, wetter conditions and a rising lake level at the end of a Holocene dry event. There is no apparent response in the chironomid assemblage, however, to burning at the onset of this dry event (c. 10,000 cal yr BP), which is the major transformative agent of the terrestrial vegetation. This study shows that chironomid assemblages in the tropical Andes responded to regional and local environmental changes, and in particular, that they were sensitive to adjustments in net moisture balance (water level fluctuations and salinity) and anthropogenic impacts (nutrient input). This suggests that within-lake processes are more important as drivers of chironomid assemblage composition than terrestrial vegetation or fire regime. Nevertheless, the full potential of subfossil chironomid analysis will only be realised once more modern autecological data are available.
Research over the past few decades has illuminated the dynamic nature of tropical palaeoclimates ... more Research over the past few decades has illuminated the dynamic nature of tropical palaeoclimates and the important role that the tropics played in global climate patters. Increasingly, the realization has grown that climate changes at high latitudes cannot simply be extrapolated into tropical regions. Rather, the tropics have sometimes led the changes or have responded to them differently when compared with their high latitude counterparts. Similarly, the tropics, spanning 46o of latitude in two hemispheres on three continents, do not respond uniformly to a given forcing. In this chapter we review evidence from the last glacial maximum (defined in the high latitude northern hemisphere) to modern, and consider features of environmental change ranging from climatic variability to extinction of megafauna.
A c. 18 ka cal BP long sediment record from Laguna Khomer Kocha Upper (4153 m asl), Bolivia, show... more A c. 18 ka cal BP long sediment record from Laguna Khomer Kocha Upper (4153 m asl), Bolivia, shows that fire regime, governed by climatic variation, has long been a transformative agent in the eastern Andes. Before c. 14.5 ka cal BP, warming and relatively moist conditions free from fire, facilitated the expansion of high Andean Polylepis woodland. Fire onset at c. 14.5.ka cal BP, quickly transformed the local vegetation and the woodlands became restricted to areas protected from fire. A major increase in burning, c. 10.1–6.4 ka cal BP removed Polylepis woodland locally and this coincided with a region-wide Holocene dry event (HDE) which caused falling lake levels and allowed fire intensification. A decline in burning at c. 6.4 ka cal BP and an increase in marsh–woodland (Alnus) marked the termination of the HDE and a return to wetter conditions. As well as recording the environmental history of local vegetation dynamics, long-distance pollen transport provides evidence of changes in the Yungas montane forests, highlighting their sensitivity to climate and burning regimes. Simultaneous adjustments in both Andean and Yungas montane taxa suggest that vegetation dynamics in the two environments are linked to a common climatic driver. There is no evidence to indicate that human activity had any impact on the local landscape.
Highlights
► Fossil pollen, charcoal and spores provided an 18 ka year record of climate change. ► Charcoal revealed that fire was a transformative agent in the eastern Andes. ► A major increase in burning occurred in the early Holocene (10.1 ka cal BP). ► Pollen and charcoal indicated a shift to wetter conditions at 6.4 ka cal BP. ► The sensitivity of Polylepis woodland to fire is confirmed.
The Cochabamba Basin (Bolivia) is on the ancient road network connecting Andean and lowland areas... more The Cochabamba Basin (Bolivia) is on the ancient road network connecting Andean and lowland areas. Little is known about the longevity of this trade route or how people responded to past environmental changes. The eastern end of the Cochabamba valley system constricts at the Vacas Lake District, constraining the road network and providing an ideal location in which to examine past human–environmental interactions. Multi-proxy analysis of sediment from Lake Challacaba has allowed a c. 4000 year environmental history to be reconstructed. Fluctuations in drought tolerant pollen taxa and calcium carbonate indicate two periods of reduced moisture availability (c. 4000–3370 and c. 2190–1020 cal yr BP) compared to adjacent wetter episodes (c. 3370–2190 and c. 1020 cal yr BP–present). The moisture fluctuations broadly correlate to El Niño/Southern Oscillation variations reported elsewhere. High charcoal abundance from c. 4000 to 2000 yr ago indicates continuous use of the ancient road network. A decline in charcoal and an increase in dung fungus (Sporormiella) c. 1340–1210 cal yr BP, suggests that cultural changes were a major factor in shaping the modern landscape. Despite undisputable impacts of human populations on the Polylepis woodlands today, we see no evidence of woodland clearance in the Challacaba record.
Puyasena et al. question our interpretation of climate-driven vegetation change on the Andean fla... more Puyasena et al. question our interpretation of climate-driven vegetation change on the Andean flank in western Amazonia during the middle Pleistocene and suggest that the use of Podocarpus spp. as a proxy of past climate change should be reassessed. We defend our assertion that vegetation change at the Erazo study site was predominantly driven by climate change due to concomitant changes recorded by multiple taxa in the fossil record.
Science, Jan 1, 2011
A reconstruction of past environmental change from Ecuador reveals the response of lower montane ... more A reconstruction of past environmental change from Ecuador reveals the response of lower montane forest on the Andean flank in western Amazonia to glacial-interglacial global climate change. Radiometric dating of volcanic ash indicates that deposition occurred ~324,000 to 193,000 years ago during parts of Marine Isotope Stages 9, 7, and 6. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest altered radically in response to glacial-interglacial climate change. The presence of Podocarpus macrofossils ~1000 meters below the lower limit of their modern distribution indicates a relative cooling of at least 5°C during glacials and persistence of wet conditions. Interglacial deposits contain thermophilic palms suggesting warm and wet climates. Hence, global temperature change can radically alter vegetation communities and biodiversity in this region.
Since the Mid Pleistocene Revolution, which occurred about one million years ago, global temperat... more Since the Mid Pleistocene Revolution, which occurred about one million years ago, global temperatures have fluctuated with a quasi-periodicity of ca. 100 ka. The pattern of past change in the extent of woodlands, and therefore by inference vegetation carbon storage, has been demonstrated to have a strong positive link with this global temperature change at high and mid latitudes. However, understanding of climate systems and ecosystem function indicates that the pattern of woodland change at low latitudes may follow a fundamentally different pattern. We present output from the intermediate complexity model GENIE-1, comprising a single transient simulation over the last 800 ka and a 174-member ensemble of 130 ka transient simulations over the last glacial cycle. These simulations suggest that while vegetation carbon storage in mid–high northern latitudes robustly follows the characteristic ca. 100 ka cycle, this signal is not a robust feature of tropical vegetation, which is subject to stronger direct forcing by the precessional (21 ka) orbital cycle (albeit with a highly uncertain response). We conclude that the correlation of palaeoenvironmental records from low latitudes with global temperature change must be done with caution.
Palaeogeography, …, Jan 1, 2011
Fossil pollen and charcoal analyses of sediments from Lake Titicaca, Peru/Bolivia, provide a reco... more Fossil pollen and charcoal analyses of sediments from Lake Titicaca, Peru/Bolivia, provide a record of palaeoclimatic variation spanning four full glacial cycles. Pollen, aquatic microfossils, and charcoal, as well as previously published data including diatom assemblages, carbonate content, and stable carbon isotopic ratios of organic carbon, indicate that interglacials were warm and dry whereas the peaks of glacials were cold and wet. Each of the interglacials documented in the record are somewhat different, with those of MIS 5e and MIS 9 inducing lower lake levels and a drier vegetation signature than those of MIS 7 and 1. The presence of charcoal particles in sediments deposited during previous interglacials provides evidence of the long-term role of fire in shaping Andean ecosystems.
Global Change Biology, Jan 1, 2010
A 370 000-year paleoecological record from Lake Titicaca provides a detailed record of past clima... more A 370 000-year paleoecological record from Lake Titicaca provides a detailed record of past climate change in which interglacial periods are seen to have some elements of commonality, but also some key differences. We advance a conceptual feedback model to account for the observed changes that includes previously ignored lake effects. Today Lake Titicaca serves to warm the local environment by about 4–5 °C and also to increase rainfall. We observe that as water levels in the lake are drawn down due to warm, dry, interglacial conditions, there is a possible regional cooling as the lake effect on local microclimates diminishes. Positive feedback mechanisms promote drying until much of the lake basin is reduced to salt marsh. Consequently, the usual concept of upslope migration of species with warming would not be applicable in the Altiplano. If, as projected, the next century brings warmer and drier conditions than those of today, a tipping point appears to exist within ca. 1–2 °C of current temperatures, where the relatively benign agricultural conditions of the northern Altiplano would be replaced by inhospitable arid climates. Such a change would have profound implications for the citizens of the Bolivian capital, La Paz.
Journal of …, Jan 1, 2009
Question: Is the modern patchy distribution of highly biodiverse Polylepis woodlands a consequenc... more Question: Is the modern patchy distribution of highly biodiverse Polylepis woodlands a consequence of human activity or, natural fluctuations in environmental conditions? What are the consequences of changing climate for the tree genus Polylepis?
Location: High central tropical Andes.
Methods: We characterise the ecological baseline conditions for Polylepis woodlands over the last ca. 370,000 years through: i) examination of fossil pollen records (Salar de Uyuni and Lake Titicaca) and, ii) a review of autecological information concerning Polylepis.
Results: Fossil pollen data reveal fluctuations in the abundance (c. 0-34%) of Polylepis pollen prior to the arrival of humans in South America (>12,000 years ago). Indicating that Polylepis did not form permanent continuous woodland prior to the arrival of humans and that climatic factors can drive rapid vegetation change. Autecological assessment of Polylepis reveals: i) negative moisture balance, ii) fire, iii) waterlogging, and iv) cloud cover to be critical to determining the niche space available for Polylepis.
Conclusions: Polylepis niche space in the central Andes was at a maximum during warm and wet conditions in the past, but might be at a minimum during the warmer and drier-than-modern conditions predicted for later this century. The sensitivity to past global climate change emphasises the need for conservation planners to consider model predictions of a warmer central Andes in the coming decades when developing planting schemes. Natural fluctuations in woodland abundance suggest the most effective way for conservation efforts to 'mimic' the natural baseline would be to develop a reproductively connected patchwork of communities.
Review of Palaeobotany and …, Jan 1, 2009
Accurate differentiation between tropical forest and savannah ecosystems in the fossil pollen rec... more Accurate differentiation between tropical forest and savannah ecosystems in the fossil pollen record is hampered by the combination of: i) poor taxonomic resolution in pollen identification, and ii) the high species diversity of many lowland tropical families, i.e. with many different growth forms living in numerous environmental settings. These barriers to interpreting the fossil record hinder our understanding of the past distributions of different Neotropical ecosystems and consequently cloud our knowledge of past climatic, biodiversity and carbon storage patterns. Modern pollen studies facilitate an improved understanding of how ecosystems are represented by the pollen their plants produce and therefore aid interpretation of fossil pollen records. To understand how to differentiate ecosystems palynologically, it is essential that a consistent sampling method is used across ecosystems. However, to date, modern pollen studies from tropical South America have employed a variety of methodologies (e.g. pollen traps, moss polsters, soil samples). In this paper, we present the first modern pollen study from the Neotropics to examine the modern pollen rain from moist evergreen tropical forest (METF), semi-deciduous dry tropical forest (SDTF) and wooded savannah (cerradão) using a consistent sampling methodology (pollen traps). Pollen rain was sampled annually in September for the years 1999-2001 from within permanent vegetation study plots in, or near, the Noel Kempff Mercado National Park (NKMNP), Bolivia. Comparison of the modern pollen rain within these plots with detailed floristic inventories allowed estimates of the relative pollen productivity and dispersal for individual taxa to be made (% pollen / % vegetation or ‘p/v’). The applicability of these data to interpreting fossil records from lake sediments was then explored by comparison with pollen assemblages obtained from five lake surface samples.
Pollen productivity is demonstrated to vary inter-annually and conforms to a consistent hierarchy for any given year: METF > SDTF > cerradão. This suggests an association between pollen productivity and basic structural characteristics of the ecosystem, i.e. closed canopy vs. open canopy vs. savannah. Comparison of modern pollen and vegetation revealed that some important floristic elements were completely absent from the pollen: Qualea and Erisma (METF), Bauhinia, Simira and Guazuma (SDTF), and Pouteria and Caryocar (cerradão). Anadenanthera was found to be abundant in both the pollen and flora of SDTF (p/v = 3.6), while Poaceae was relatively poorly represented in cerradão (0.2). Moraceae, Cecropia and Schefflera were found to be over-represented palynologically in all ecosystems. Overall, the data demonstrated that no one taxon could be used as a definitive indicator of any of the ecosystems. Instead, associations of taxa were found to be important: METF = Moraceae (>40%), Cecropia, Hyeronima, Celtis; SDTF = Anadenanthera, Apuleia, Ferdinandusa and non-arboreal Asteraceae, Bromeliaceae, Piper and fern spores; cerradão = Poaceae, Myrtaceae, Borreria, Solanum plus Asteraceae and fern spores. Interpretation of Poaceae pollen was highlighted as problematic, with relatively low abundance in the cerradão (<20%) in comparison to high abundance in lake environments (c. 30-50%). Re-examination of fossil pollen records from NKMNP revealed that modern vegetation associations were only established in the last few thousand years.
Climate of the Past …, Jan 1, 2009
Palaeogeography, Palaeoclimatology, …, Jan 1, 2007
Palaeogeography, …, Jan 1, 2008
A palynological investigation of the last glacial-interglacial cycle in the southern hemisphere t... more A palynological investigation of the last glacial-interglacial cycle in the southern hemisphere tropical Andes reveals changes in the moisture balance as the main driver in vegetation change. Thirty accelerator mass spectrometry radiocarbon dates, biostratigraphy and tephra correlation reveal that a 119 m sediment core recovered from the Huiñaimarca sub-basin of Lake Titicaca (16.0° to 17.5° S, 68.5° to 70° W; 3810 masl) contains sediments covering > 151,000 years. Correlation of aridity indicators with precessional variations in insolation is used to fine tune the structure of the age-depth curve within this period.
Variations in Isoëtes concentration (above/below 10,000 grains/cm3) identify the extent of shallow water environments. Examination of another palaeolimnological indicator (Pediastrum) and consideration of the bathymetry of the Huiñaimarca sub-basin allow the reconstruction of lake-level fluctuations. These data indicate five wet/dry cycles between c. 151,000 and 14,200 cal yr BP. High stands are suggested during the transition into (c. 134,000 cal yr BP), and out of (c. 114,000 and 92,000 cal yr BP), the last interglacial, and during full glacial conditions (c. 70,000 and 45,000 cal yr BP). These cycles are superimposed on a general trend of deepening lake levels through the glacial period.
This interpretation is supported by correlation with sediments from Salar de Uyuni (20°S, 68°W; 3653 masl). The youngest wet episode is concurrent with palaeolake Minchin (c. 45,000 cal yr BP), with further evidence for an additional wet period commencing c. 28,000 cal yr BP, concomitant with palaeolake Tauca. The timing of lake level fluctuations is also supported by palaeoshoreline reconstructions from the Uyuni-Poopó region. However, our data do not suggest a major peak in lake level in Huiñaimarca during the Ouki lake cycle (c. 120,000–98,000 cal yr BP) as inferred from U–Th ages obtained from palaeoshorelines around Lago Poopó. The most extreme dry event occurs during the last interglacial period and resulted in a sedimentary hiatus tentatively dated to c. 121,000–129,000 cal yr BP.
The observed wet/dry cycles are shown to have a marked and rapid impact on the vegetation. The aridity of the last interglacial promoted a community dominated by Chenopodiaceae/Amaranthacae, with no modern Andean analogue. Polylepis/Acaena pollen is also shown to fluctuate markedly (0–20%), particularly during the transitions into, and out of, the last interglacial. It is probable that this pollen taxon is primarily representative of the high altitude arboreal genus Polylepis, which is a key component of highly biodiverse Andean woodlands today. Rapid fluctuations indicate the sensitivity of this ecosystem to natural environmental pressure and potential vulnerability to future human impact and climate change.
The 100,000 year (eccentricity) solar cycle is shown to be the major controlling factor in moisture balance and vegetation over the last glacial-interglacial cycle. However, significant fluctuations in moisture balance are also evident on timescales considerably shorter than the full glacial-interglacial cycle. We have linked these to precessional (21,000 year) forcing. Nevertheless, precise independent dating during the full glacial cycle is required to confirm the importance of this forcing mechanism.
… of the Royal …, Jan 1, 2007
While large-scale pre-Columbian human occupation and ecological disturbance have been demonstrate... more While large-scale pre-Columbian human occupation and ecological disturbance have been demonstrated close to major Amazonian waterways, less is known of sites in terra firme settings. Palaeoecological analyses of two lake districts in central and western Amazonia reveal long histories of occupation and land use. At both locations, human activity was centred on one of the lakes, while the others were either lightly used or unused. These analyses indicate that the scale of human impacts in these terra firme settings is localized and probably strongly influenced by the presence of a permanent open-water body. Evidence is found of forest clearance and cultivation of maize and manioc. These data are directly relevant to the resilience of Amazonian conservation, as they do not support the contention that all of Amazonia is a ‘built landscape’ and therefore a product of past human land use.
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Books by William Gosling
Every single day we come face-to-face with nature’s remarkable diversity, but often don’t even realize it. From the plant and animal products that make up our breakfast to the ecosystems that help to produce clean water, our very survival depends upon the variety of plant and animal life on our planet.
Crucially, Fragile Web also examines what can be done to protect the natural world and why it matters. Although we cannot undo all that we have done, ignoring the current crisis for biodiversity could fundamentally change the lives of future generations.
Fully illustrated with colour photographs, diagrams and maps, this book is a timely snapshot of the state of life on Earth.
Papers by William Gosling
Highlights
► Fossil pollen, charcoal and spores provided an 18 ka year record of climate change. ► Charcoal revealed that fire was a transformative agent in the eastern Andes. ► A major increase in burning occurred in the early Holocene (10.1 ka cal BP). ► Pollen and charcoal indicated a shift to wetter conditions at 6.4 ka cal BP. ► The sensitivity of Polylepis woodland to fire is confirmed.
Location: High central tropical Andes.
Methods: We characterise the ecological baseline conditions for Polylepis woodlands over the last ca. 370,000 years through: i) examination of fossil pollen records (Salar de Uyuni and Lake Titicaca) and, ii) a review of autecological information concerning Polylepis.
Results: Fossil pollen data reveal fluctuations in the abundance (c. 0-34%) of Polylepis pollen prior to the arrival of humans in South America (>12,000 years ago). Indicating that Polylepis did not form permanent continuous woodland prior to the arrival of humans and that climatic factors can drive rapid vegetation change. Autecological assessment of Polylepis reveals: i) negative moisture balance, ii) fire, iii) waterlogging, and iv) cloud cover to be critical to determining the niche space available for Polylepis.
Conclusions: Polylepis niche space in the central Andes was at a maximum during warm and wet conditions in the past, but might be at a minimum during the warmer and drier-than-modern conditions predicted for later this century. The sensitivity to past global climate change emphasises the need for conservation planners to consider model predictions of a warmer central Andes in the coming decades when developing planting schemes. Natural fluctuations in woodland abundance suggest the most effective way for conservation efforts to 'mimic' the natural baseline would be to develop a reproductively connected patchwork of communities.
Pollen productivity is demonstrated to vary inter-annually and conforms to a consistent hierarchy for any given year: METF > SDTF > cerradão. This suggests an association between pollen productivity and basic structural characteristics of the ecosystem, i.e. closed canopy vs. open canopy vs. savannah. Comparison of modern pollen and vegetation revealed that some important floristic elements were completely absent from the pollen: Qualea and Erisma (METF), Bauhinia, Simira and Guazuma (SDTF), and Pouteria and Caryocar (cerradão). Anadenanthera was found to be abundant in both the pollen and flora of SDTF (p/v = 3.6), while Poaceae was relatively poorly represented in cerradão (0.2). Moraceae, Cecropia and Schefflera were found to be over-represented palynologically in all ecosystems. Overall, the data demonstrated that no one taxon could be used as a definitive indicator of any of the ecosystems. Instead, associations of taxa were found to be important: METF = Moraceae (>40%), Cecropia, Hyeronima, Celtis; SDTF = Anadenanthera, Apuleia, Ferdinandusa and non-arboreal Asteraceae, Bromeliaceae, Piper and fern spores; cerradão = Poaceae, Myrtaceae, Borreria, Solanum plus Asteraceae and fern spores. Interpretation of Poaceae pollen was highlighted as problematic, with relatively low abundance in the cerradão (<20%) in comparison to high abundance in lake environments (c. 30-50%). Re-examination of fossil pollen records from NKMNP revealed that modern vegetation associations were only established in the last few thousand years.
Variations in Isoëtes concentration (above/below 10,000 grains/cm3) identify the extent of shallow water environments. Examination of another palaeolimnological indicator (Pediastrum) and consideration of the bathymetry of the Huiñaimarca sub-basin allow the reconstruction of lake-level fluctuations. These data indicate five wet/dry cycles between c. 151,000 and 14,200 cal yr BP. High stands are suggested during the transition into (c. 134,000 cal yr BP), and out of (c. 114,000 and 92,000 cal yr BP), the last interglacial, and during full glacial conditions (c. 70,000 and 45,000 cal yr BP). These cycles are superimposed on a general trend of deepening lake levels through the glacial period.
This interpretation is supported by correlation with sediments from Salar de Uyuni (20°S, 68°W; 3653 masl). The youngest wet episode is concurrent with palaeolake Minchin (c. 45,000 cal yr BP), with further evidence for an additional wet period commencing c. 28,000 cal yr BP, concomitant with palaeolake Tauca. The timing of lake level fluctuations is also supported by palaeoshoreline reconstructions from the Uyuni-Poopó region. However, our data do not suggest a major peak in lake level in Huiñaimarca during the Ouki lake cycle (c. 120,000–98,000 cal yr BP) as inferred from U–Th ages obtained from palaeoshorelines around Lago Poopó. The most extreme dry event occurs during the last interglacial period and resulted in a sedimentary hiatus tentatively dated to c. 121,000–129,000 cal yr BP.
The observed wet/dry cycles are shown to have a marked and rapid impact on the vegetation. The aridity of the last interglacial promoted a community dominated by Chenopodiaceae/Amaranthacae, with no modern Andean analogue. Polylepis/Acaena pollen is also shown to fluctuate markedly (0–20%), particularly during the transitions into, and out of, the last interglacial. It is probable that this pollen taxon is primarily representative of the high altitude arboreal genus Polylepis, which is a key component of highly biodiverse Andean woodlands today. Rapid fluctuations indicate the sensitivity of this ecosystem to natural environmental pressure and potential vulnerability to future human impact and climate change.
The 100,000 year (eccentricity) solar cycle is shown to be the major controlling factor in moisture balance and vegetation over the last glacial-interglacial cycle. However, significant fluctuations in moisture balance are also evident on timescales considerably shorter than the full glacial-interglacial cycle. We have linked these to precessional (21,000 year) forcing. Nevertheless, precise independent dating during the full glacial cycle is required to confirm the importance of this forcing mechanism.
Every single day we come face-to-face with nature’s remarkable diversity, but often don’t even realize it. From the plant and animal products that make up our breakfast to the ecosystems that help to produce clean water, our very survival depends upon the variety of plant and animal life on our planet.
Crucially, Fragile Web also examines what can be done to protect the natural world and why it matters. Although we cannot undo all that we have done, ignoring the current crisis for biodiversity could fundamentally change the lives of future generations.
Fully illustrated with colour photographs, diagrams and maps, this book is a timely snapshot of the state of life on Earth.
Highlights
► Fossil pollen, charcoal and spores provided an 18 ka year record of climate change. ► Charcoal revealed that fire was a transformative agent in the eastern Andes. ► A major increase in burning occurred in the early Holocene (10.1 ka cal BP). ► Pollen and charcoal indicated a shift to wetter conditions at 6.4 ka cal BP. ► The sensitivity of Polylepis woodland to fire is confirmed.
Location: High central tropical Andes.
Methods: We characterise the ecological baseline conditions for Polylepis woodlands over the last ca. 370,000 years through: i) examination of fossil pollen records (Salar de Uyuni and Lake Titicaca) and, ii) a review of autecological information concerning Polylepis.
Results: Fossil pollen data reveal fluctuations in the abundance (c. 0-34%) of Polylepis pollen prior to the arrival of humans in South America (>12,000 years ago). Indicating that Polylepis did not form permanent continuous woodland prior to the arrival of humans and that climatic factors can drive rapid vegetation change. Autecological assessment of Polylepis reveals: i) negative moisture balance, ii) fire, iii) waterlogging, and iv) cloud cover to be critical to determining the niche space available for Polylepis.
Conclusions: Polylepis niche space in the central Andes was at a maximum during warm and wet conditions in the past, but might be at a minimum during the warmer and drier-than-modern conditions predicted for later this century. The sensitivity to past global climate change emphasises the need for conservation planners to consider model predictions of a warmer central Andes in the coming decades when developing planting schemes. Natural fluctuations in woodland abundance suggest the most effective way for conservation efforts to 'mimic' the natural baseline would be to develop a reproductively connected patchwork of communities.
Pollen productivity is demonstrated to vary inter-annually and conforms to a consistent hierarchy for any given year: METF > SDTF > cerradão. This suggests an association between pollen productivity and basic structural characteristics of the ecosystem, i.e. closed canopy vs. open canopy vs. savannah. Comparison of modern pollen and vegetation revealed that some important floristic elements were completely absent from the pollen: Qualea and Erisma (METF), Bauhinia, Simira and Guazuma (SDTF), and Pouteria and Caryocar (cerradão). Anadenanthera was found to be abundant in both the pollen and flora of SDTF (p/v = 3.6), while Poaceae was relatively poorly represented in cerradão (0.2). Moraceae, Cecropia and Schefflera were found to be over-represented palynologically in all ecosystems. Overall, the data demonstrated that no one taxon could be used as a definitive indicator of any of the ecosystems. Instead, associations of taxa were found to be important: METF = Moraceae (>40%), Cecropia, Hyeronima, Celtis; SDTF = Anadenanthera, Apuleia, Ferdinandusa and non-arboreal Asteraceae, Bromeliaceae, Piper and fern spores; cerradão = Poaceae, Myrtaceae, Borreria, Solanum plus Asteraceae and fern spores. Interpretation of Poaceae pollen was highlighted as problematic, with relatively low abundance in the cerradão (<20%) in comparison to high abundance in lake environments (c. 30-50%). Re-examination of fossil pollen records from NKMNP revealed that modern vegetation associations were only established in the last few thousand years.
Variations in Isoëtes concentration (above/below 10,000 grains/cm3) identify the extent of shallow water environments. Examination of another palaeolimnological indicator (Pediastrum) and consideration of the bathymetry of the Huiñaimarca sub-basin allow the reconstruction of lake-level fluctuations. These data indicate five wet/dry cycles between c. 151,000 and 14,200 cal yr BP. High stands are suggested during the transition into (c. 134,000 cal yr BP), and out of (c. 114,000 and 92,000 cal yr BP), the last interglacial, and during full glacial conditions (c. 70,000 and 45,000 cal yr BP). These cycles are superimposed on a general trend of deepening lake levels through the glacial period.
This interpretation is supported by correlation with sediments from Salar de Uyuni (20°S, 68°W; 3653 masl). The youngest wet episode is concurrent with palaeolake Minchin (c. 45,000 cal yr BP), with further evidence for an additional wet period commencing c. 28,000 cal yr BP, concomitant with palaeolake Tauca. The timing of lake level fluctuations is also supported by palaeoshoreline reconstructions from the Uyuni-Poopó region. However, our data do not suggest a major peak in lake level in Huiñaimarca during the Ouki lake cycle (c. 120,000–98,000 cal yr BP) as inferred from U–Th ages obtained from palaeoshorelines around Lago Poopó. The most extreme dry event occurs during the last interglacial period and resulted in a sedimentary hiatus tentatively dated to c. 121,000–129,000 cal yr BP.
The observed wet/dry cycles are shown to have a marked and rapid impact on the vegetation. The aridity of the last interglacial promoted a community dominated by Chenopodiaceae/Amaranthacae, with no modern Andean analogue. Polylepis/Acaena pollen is also shown to fluctuate markedly (0–20%), particularly during the transitions into, and out of, the last interglacial. It is probable that this pollen taxon is primarily representative of the high altitude arboreal genus Polylepis, which is a key component of highly biodiverse Andean woodlands today. Rapid fluctuations indicate the sensitivity of this ecosystem to natural environmental pressure and potential vulnerability to future human impact and climate change.
The 100,000 year (eccentricity) solar cycle is shown to be the major controlling factor in moisture balance and vegetation over the last glacial-interglacial cycle. However, significant fluctuations in moisture balance are also evident on timescales considerably shorter than the full glacial-interglacial cycle. We have linked these to precessional (21,000 year) forcing. Nevertheless, precise independent dating during the full glacial cycle is required to confirm the importance of this forcing mechanism.