Lindsey Gillson

Looking forward through the past : identification of 50 priority research questions in palaeoecology

Summary 1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on timescales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. This article is protected by copyright. All rights reserved. Accepted Article 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human–environment interactions in the Anthropocene; biodiversity, conservation, and novel ecosystems; biodiversity over long timescales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes, and the continued application of long-term data for better-informed landscape management. 7. Synthesis Palaeoecology is a vibrant and thriving discipline and these 50 priority questions highlight its potential for addressing both pure (e.g. ecological and evolutionary, methodological) and applied (e.g. environmental and conservation) issues related to ecological science and global change.

Evidence of Hierarchical Patch Dynamics in an East African savanna

The Hierarchical Patch Dynamics Paradigm provides a conceptual framework for linking pattern, process and scale in ecosystems, but there have been few attempts to test this theory because most ecological studies focus on only one spatial scale, or are limited in their temporal scope. Here I use palaeoecological techniques (analysis of fossil pollen and stable carbon isotopes) to compare vegetation heterogeneity in an east African savanna at three spatial scales, over hundreds of years. The data show that patterns of vegetation change are different at the three spatial scales of observation, and suggest that different ecological processes dominate tree abundance at micro, local and landscape scales. Interactions between plants, disturbance (e.g., by fire and herbivores), climate and soil type may influence tree density at differing spatial and temporal scales. This hierarchical explanation of savanna vegetation dynamics could inform future biodiversity conservation and management in savannas.

Testing the sensitivity of charcoal as an indicator of fire events in savanna environments: quantitative predictions of fire proximity, area and intensity

The charcoal record contained in lake sedimentary sequences is often used to infer past fire events. Studies to calibrate such charcoal records have been carried out in a range of mid- to high-latitude regions and relationships have been determined between size and quantity of charcoal in the sediment and proximity and spatial extent of the fires. Very little is known, however, about the relationship between fire events in savanna ecosystems and how these are represented in the charcoal record in lake sedimentary sequences. This study presents the results of a project that aimed to calibrate the micro- and macroscopic charcoal record from Kruger National Park, South Africa, with known fire events. Surface sediment samples were analysed for charcoal of different size classes and compared with data on fire proximity, area and intensity (the rate of energy released along a fire front) from fire events over the last 10 years, and the relevant source areas for micro- and macroscopic charcoal were quantified. Results indicated that (i) the Relevant Source Area of Charcoal for lakes c. 200 m diameter is between 0 and 5 km for charcoal particles >50 ∝m in length and between 10 and 15 km for charcoal particles <50 ∝m; (ii) that charcoal deposits are most likely to represent combined fire events from the preceding five years; (iii) that fire proximity, area and intensity are each significantly represented in the charcoal record, but not equally, as the signal resulting from fire intensity is stronger than that for fire proximity or area. Mathematical equations linking charcoal with fire proximity, area and intensity are presented.

Thresholds of potential concern as benchmarks in the management of African savannahs

In the Kruger National Park (KNP), South Africa, ecosystem managers use a series of monitoring endpoints, known as thresholds of potential concern (TPCs), to define the upper and the lower levels of accepted variation in ecosystems. For woody vegetation, the current TPC suggests that woody cover should not drop by more than 80% of its ‘highest ever’ value. In this paper, we explore the utility of palaeoecological data in informing TPCs. We use calibrated fossil pollen data to explore variability in vegetation at two sites over the past 5000 years, to provide a long-term record of changes in woody vegetation cover and a context for interpreting more recent vegetation change. The fossil pollen data are calibrated using studies of modern pollen and vegetation from KNP; arboreal pollen percentage was simulated using pollen–landscape modelling software for savannah landscapes of varying woody vegetation cover, and the relationship between vegetation and pollen data was quantified using nonlinear regression. This quadratic equation was then applied to fossil pollen data in order to estimate woody vegetation cover from arboreal pollen percentages. Our results suggest that the TPCs have not been exceeded during the period represented in the pollen record, because estimated woody vegetation cover has remained above 20% of its highest ever value. By comparing the fossil pollen data with TPCs, our study demonstrates how palaeoecological data can be presented in a form that is directly relevant to management objectives.

How does spatial heterogeneity influence resilience to climatic changes? Ecological dynamics in southeast Madagascar.

Conceptual models suggest a link between spatial heterogeneity, diversity, and resilience, but few empirical studies exist to demonstrate such an ecological relationship. In this study, we investigated the nature of spatial heterogeneity and resilience of two forest fragments from Madagascars highly endangered littoral forest, and two nearby sites in the surrounding ericoid grassland. This ecosystem has been subjected to a number of large environmental disturbances over the last 6000 years, including a late Holocene sea-level rise of 1–3 m above the present level, pronounced drought events, and natural and anthropogenic fires. The aims were to determine the driving mechanisms for heterogeneity and to compare the impact of large environmental disturbances among the four sites. Overall, our results indicate that, contrary to previous assumptions of continuous forest cover, the ecosystem was already spatially heterogeneous prior to the arrival of humans. Differences in groundwater, nutrients, and fires main...

From myopia to clarity: sharpening the focus of ecosystem management through the lens of palaeoecology.

Maintaining biodiversity and ecosystem services in a changing environment requires a temporal perspective that informs realistic restoration and management targets. Such targets need to be dynamic, adaptive, and responsive to changing boundary conditions. However, the application of long-term data from palaeoecology is often hindered as the management and policy implications are not made explicit, and because data sets are often not accessible or amenable to stakeholders. Focussing on this translation gap, we explore how a palaeoecological perspective can change the focus of biodiversity management and conservation policy. We embed a long-term perspective (decades to millennia) into current adaptive management and policy frameworks, with the aim of encouraging better integration between palaeoecology, conservation management, and mainstreaming viable provision of ecosystem services.

Ivory and ecology—changing perspectives on elephant management and the international trade in ivory

Abstract This paper provides an analysis of the ecological ideas which underpin policies of elephant management and ivory trading in African elephant range states. Increasingly, the discussion surrounding the international trade in ivory has focussed on potential revenue that could be generated from the sale of stock-piled ivory and other products derived from elephants. However, the international trade in ivory is regulated by Convention on International Trade in Endangered Species (CITES), which recognises that “international co-operation is essential for the protection of certain species of wild fauna and flora against over-exploitation through international trade”. Thus, the arguments in favour of ivory trading must refer to conservation objectives, and controversies over the ivory trade have become linked to debates over the management of elephant populations, and ecological assumptions regarding elephant habitat and the resilience or otherwise of savanna ecosystems. In this paper, we examine the ecological aspects of the arguments for a legalised international trade in ivory, and discuss how advances in ecological understanding could influence future discussion of this controversial issue.

Demything “wilderness”: implications for protected area designation and management

Protected areas are a cornerstone of many conservation approaches, and concepts of pristineness and wilderness are often considered central to protected area designation and management. However, these concepts are rarely explored through a historical lens that captures the philosophies and assumptions underlying protected area designation. In this paper, we aim to improve our understanding of protected area designation and management by reviewing the history of four main conservation approaches: (1) Wilderness conservation and the Yellowstone Model; (2) Wise use and the Game Reserve Model; (3) Wildlife and Biodiversity conservation; and (4) Ecosystem management. Through examination of the history of these Models, we discuss the values, rationale and assumptions behind each approach, and how these interface with protected area designation. In each case, we explore the extent of dependence on concepts of wilderness and pristineness. We also highlight the evolution of alternative criteria for designating protected areas, and ascertain how far these alternative values influence protected area designation and management.

The (im)balance of nature: a public perception time-lag?

The last two decades have seen a conceptual shift within environmental and social sciences from an emphasis on ecosystem stability and balance to an acknowledgement of the importance of flux and change in the natural world. This has profound implications for conservation management and policy and has driven an (incomplete) transition from managing to maintain (bio)diversity and ecological stability at some historically derived “optimum” to managing to maintain important ecosystem and evolutionary processes such as nutrient cycles and migration. Here, we investigate whether this change from a “balance of nature” metaphor to a more dynamic perspective (“flux of nature”) is reflected in the representation of conservation and ecosystem management in the news media, the Internet, and the academic literature. We found that the media and the global Internet community still portray the aim of conservation science and of conservationists as being one of maintaining stability, harmony and balance.

Resilience and Thresholds in Savannas: Nitrogen and Fire as Drivers and Responders of Vegetation Transition

Resilience theory suggests that ecosystems can persist for long periods, before changing rapidly to a new vegetation phase. Transition between phases occurs when ecological thresholds have been crossed, and is followed by a reorganization of biotic and environmental interactions, leading to the emergence of a new vegetation phase or quasi-stable state. Savannas are dynamic, complex systems in which fire, herbivory, water and nutrient availability interact to determine tree abundance. Phase and transition has been observed in savannas, but the role of these different possible drivers is not always clear. In this study, our objectives were to identify phase and transition in the fossil pollen record, and then to explore the role of nitrogen and fire in these transitions using δ15N isotopes and charcoal abundance. We present palaeoenvironmental data from the Kruger National Park, South Africa, which show transition between grassland and savanna phases. Our results show transition at the end of the ninth century A.D. from a nutrient- and herbivore-limited grazing lawn, in which fire was absent and C4 grasses were the dominant and competitively superior plant form, to a water-, fire- and herbivory-limited semi-arid savanna, in which C4 grasses and C3 trees and shrubs co-existed. The data accord with theoretical frameworks that predict that variability in ecosystems clusters in regions of higher probability space, interspersed by rapid transitions between these phases. The data are also consistent with the idea that phase transitions involve switching between different dominant driving processes or limiting factors.