Cynthia A. Froyd

How can a knowledge of the past help to conserve the future? Biodiversity conservation and the relevance of long-term ecological studies

This paper evaluates how long-term records could and should be utilized in conservation policy and practice. Traditionally, there has been an extremely limited use of long-term ecological records (greater than 50 years) in biodiversity conservation. There are a number of reasons why such records tend to be discounted, including a perception of poor scale of resolution in both time and space, and the lack of accessibility of long temporal records to non-specialists. Probably more important, however, is the perception that even if suitable temporal records are available, their roles are purely descriptive, simply demonstrating what has occurred before in Earths history, and are of little use in the actual practice of conservation. This paper asks why this is the case and whether there is a place for the temporal record in conservation management. Key conservation initiatives related to extinctions, identification of regions of greatest diversity/threat, climate change and biological invasions are addressed. Examples of how a temporal record can add information that is of direct practicable applicability to these issues are highlighted. These include (i) the identification of species at the end of their evolutionary lifespan and therefore most at risk from extinction, (ii) the setting of realistic goals and targets for conservation ‘hotspots’, and (iii) the identification of various management tools for the maintenance/restoration of a desired biological state. For climate change conservation strategies, the use of long-term ecological records in testing the predictive power of species envelope models is highlighted, along with the potential of fossil records to examine the impact of sea-level rise. It is also argued that a long-term perspective is essential for the management of biological invasions, not least in determining when an invasive is not an invasive. The paper concludes that often inclusion of a long-term ecological perspective can provide a more scientifically defensible basis for conservation decisions than the one based only on contemporary records. The pivotal issue of this paper is not whether long-term records are of interest to conservation biologists, but how they can actually be utilized in conservation practice and policy.

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.

Fossil Pollen as a Guide to Conservation in the Galápagos

Paleoecological evidence from the past 8000 years in the Galápagos Islands shows that six presumed introduced or doubtfully native species (Ageratum conyzoides, Borreria laevis/Diodia radula‐type, Brickellia diffusa, Cuphea carthagenensis, Hibiscus diversifolius, and Ranunculus flagelliformis) are in fact native to the archipelago. Fossil pollen and macrofossils from four sites in the highlands of Santa Cruz Island reveal that all were present thousands of years before the advent of human impact, refuting their classification as introduced species. These findings have substantial implications not only for conservation in Galápagos but for the management of introduced species and pantropical weeds in general.

FOSSIL STOMATA REVEAL EARLY PINE PRESENCE IN SCOTLAND: IMPLICATIONS FOR POSTGLACIAL COLONIZATION ANALYSES

The analysis of fossil stomata reveals the early postglacial presence of Pinus sylvestris at two sites in the Scottish Highlands, 1600 and 600 years prior to the arrival times indicated by traditional palynological methods. Fossil stomata provide unambiguous evidence of past local presence for Pinus sylvestris, which produces abundant and widely dispersed pollen, revealing its presence when pine pollen frequencies are as low as 0.4%, considerably below the commonly adopted minimum frequency threshold of 20%. Thus a species may be present for hundreds to thousands of years before expansion of the local population is registered in the palynological record. This has significant implications, not only for the initial spread of pine throughout the British Isles, but more generally for analyses of the continental-scale migration of temperate and boreal forest taxa based on palynological data. Failure to differentiate effectively among the processes of arrival, establishment, and expansion in analyses of plant migration rates and patterns means that many existing reconstructions of postglacial colonization may, in actuality, represent the expansion of populations over time, rather than the initial spread of species.

Holocene palaeo-invasions: the link between pattern, process and scale in invasion ecology?

Invasion ecology has made rapid progress in recent years through synergies with landscape ecology, niche theory, evolutionary ecology and the ecology of climate change. The palaeo-record of Holocene invasions provides a rich but presently underexploited resource in exploring the pattern and process of invasions through time. In this paper, examples from the palaeo-literature are used to illustrate the spread of species through time and space, also revealing how interactions between invader and invaded communities change over the course of an invasion. The main issues addressed are adaptation and plant migration, ecological and evolutionary interactions through time, disturbance history and the landscape ecology of invasive spread. We consider invasions as a continuous variable, which may be influenced by different environmental or ecological variables at different stages of the invasion process, and we use palaeoecological examples to describe how ecological interactions change over the course of an invasion. Finally, the use of palaeoecological information to inform the management of invasions for biodiversity conservation is discussed.

The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity

The giant tortoises of the Galápagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelagos only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500–700 years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subsequently leading to the decline of several now-rare or extinct plant species.

A quantitative framework for analysis of regime shifts in a Galápagos coastal lagoon

Regime shifts are often used to describe sharp changes between two or more ecological states, each characterized by their own dynamics, stochastic fluctuations, or cycles. Ecological theory indicates they can occur either as a result of an abrupt environmental forcing (extrinsic regime shift), or be indicative of complex responses to local-scale dynamics and thresholds (intrinsic regime shift). One important area of ecological research is to develop quantitative tools to analyze regime shifts, but there are few studies that have applied these methods to the long-term ecological record. In this study, we introduce a framework to investigate regime shifts in diatom assemblages and mangrove ecosystem dynamics in a coastal lagoon from the Galapagos Islands over the past 2600 years. The framework integrates a set of established statistical methodologies for investigating regime shift dynamics in long-term ecological records. We use these methods to (1) identify the presence of regime shifts; (2) test for a ser...

Detecting the provenance of Galápagos non-native pollen: the role of humans and air currents as transport mechanisms.

The influence of non-native pollen, both long-distance transported and from introduced taxa, on reconstruction of past vegetation is not often well quantified in palynological investigations. We examined both fossil and modern samples from the Galápagos Islands, a remote archipelago lying 1000 km from the nearest continent. These islands are particularly well-suited for such an assessment, as (1) the native flora is limited and well-known, enabling increased taxonomic resolution within the palynological record, and (2) human impact in the Galápagos started after discovery by Europeans in 1535, allowing clear distinctions to be made between native and introduced taxa. Pollen samples were collected from five profiles in the Galápagos and grouped in (a) a pre-human-impact period, (b) an early human-impact period after c. 1535, and (c) a late human-impact period after c. 1973 when the introduced Cinchona pubescens tree started to expand. Introduced taxa accounted for approximately 10% of total pollen (excluding Cyperaceae) throughout the human-impact periods and long-distance transported pollen for approximately 5%. Twenty pollen taxa of introduced plants were found. Cinchona, which grows abundantly near the study sites, accounted for most of the introduced pollen, but an appreciable part also came from introduced plants growing in low numbers and at more distant locations within the archipelago. Total long-distance transported pollen (35 taxa) increased from 3% of total pollen in the pre-human-impact period to 5% in the human-impact periods, probably due to destruction of native vegetation through fire and thus reduction of local pollen production. These phenomena might lead to erroneous interpretation of local plant occurrence when the native/non-native or local/extra-local status of plants is not known.

Ecosystem Resilience and Threshold Response in the Galápagos Coastal Zone

Background The Intergovernmental Panel on Climate Change (IPCC) provides a conservative estimate on rates of sea-level rise of 3.8 mm yr−1 at the end of the 21st century, which may have a detrimental effect on ecologically important mangrove ecosystems. Understanding factors influencing the long-term resilience of these communities is critical but poorly understood. We investigate ecological resilience in a coastal mangrove community from the Galápagos Islands over the last 2700 years using three research questions: What are the ‘fast and slow’ processes operating in the coastal zone? Is there evidence for a threshold response? How can the past inform us about the resilience of the modern system? Methodology/Principal Findings Palaeoecological methods (AMS radiocarbon dating, stable carbon isotopes (δ13C)) were used to reconstruct sedimentation rates and ecological change over the past 2,700 years at Diablas lagoon, Isabela, Galápagos. Bulk geochemical analysis was also used to determine local environmental changes, and salinity was reconstructed using a diatom transfer function. Changes in relative sea level (RSL) were estimated using a glacio-isostatic adjustment model. Non-linear behaviour was observed in the Diablas mangrove ecosystem as it responded to increased salinities following exposure to tidal inundations. A negative feedback was observed which enabled the mangrove canopy to accrete vertically, but disturbances may have opened up the canopy and contributed to an erosion of resilience over time. A combination of drier climatic conditions and a slight fall in RSL then resulted in a threshold response, from a mangrove community to a microbial mat. Conclusions/Significance Palaeoecological records can provide important information on the nature of non-linear behaviour by identifying thresholds within ecological systems, and in outlining responses to ‘fast’ and ‘slow’ environmental change between alternative stable states. This study highlights the need to incorporate a long-term ecological perspective when designing strategies for maximizing coastal resilience.

Temporal stability in bristlecone pine tree-ring stable oxygen isotope chronologies over the last two centuries:

The absolutely dated bristlecone pine (Pinus longaeva) tree-ring chronology spans almost 9000 years, offering great potential for inferring past environmental change. Existing ring width chronologies have been widely used to produce some of the most influential millennial length temperature reconstructions for the Northern Hemisphere. A recently published δ 18O record from two bristlecone pine trees growing at Methuselah Walk in the White Mountains of California showed a dramatic decrease in δ 18O between AD 1850 and 1920 (c. 13‰), interpreted as indicating a major shift in Pacific storm tracks over the past 300 years. Here we present new bristlecone pine δ18O time series from 15 trees at three White Mountains sites, including two series from Methuselah Walk. Whilst occasional high interannual variability is observed in our δ 18O series, none of our chronologies exhibit an equivalent pronounced or sustained twentieth-century decrease, suggesting the earlier results are anomalous and may require palaeoclimatic re-interpretation.