Historic Molecules Connect the Past to Modern Conservation
Abstract and Keywords
This chapter explores the use of isotope analysis to bridge the knowledge gap between contemporary wildlife conservation management and the ecology of the African elephant in its historic landscape. Case studies from eastern and southern Africa focus on isotope analysis as it has been used to understand diet, movement, and environmental conditions of elephant populations over longer time scales than is possible with observational studies. These case studies provide support for the applied use of historical ecological data to make a substantial impact on the modern conservation of the elephant in its landscape. Although this chapter is specific to African elephants, it is possible to apply the methodology and approach to other species and in different landscapes across the world.
Wildlife conservation policies can (and should) be enlightened by the long-term perspective offered by historic isotope data collected by archaeologists and palaeoecologists. These data can provide a historic lens on the establishment, disturbance, and recovery of ecosystems as well as an understanding of human–animal interactions from the past to the present. Though historical and archaeological data sets are often fragmentary, there is a real benefit to using historic isotope data in conjunction with modern data, as this offers a more complete understanding of how the ecology of specific landscapes and species have changed over various time scales. These time scales can range from the last few decades, as in the case of Jaeger and Cherel’s (2011) isotopic study of penguin diets in the southern Indian Ocean, to the past few hundred years, as in the case of Blight et al.’s (2014) study of gulls in North America, to more than 10,000 years in the case of Fox-Dobbs et al.’s (2007) study of late Pleistocene carnivore palaeoecology from the La Brea tar pits.
This chapter briefly summarizes the principles of isotope analysis, and presents a set of case studies illustrating the use of this technique with a focus on elephant conservation in eastern and southern Africa (Fig. 11.1). One of the foremost concerns for managing modern African elephant populations involves distributions and their impact on the surrounding habitat for humans and other flora and fauna that share that habitat. Therefore, there is a particular focus in this chapter on the technique of isotope analysis as it has been applied to understand the dietary changes in elephant populations over historic time scales (circa the last 150 years). The focus is on African elephants due to the fact that the conservation of this species is arguably one of the most pressing (p. 209) international concerns within wildlife ecology, and is the subject of what is currently the longest palaeodietary study using isotope analysis of animal tissue (Codron et al., 2012). Although this chapter is specific to African elephants, it is possible to apply the methodology and approach to other species and in different landscapes across the world (Fox-Dobbs et al., 2012; Jennings et al., 2002; Koch et al., 2009; Moss et al., 2006; Szpak et al., 2012).
Fundamentals of the Method
Each time an animal eats, drinks, or moves across the landscape, it incorporates elements into its body that become the building blocks of tissue such as hair, bone, and teeth. These elements are ingested from water, soil, and food, and are all traceable in biological tissues after death as long as those tissues are preserved after death. Thus, the isotope composition of animal tissues are affected by many factors, including the type of environment in which the animal lives, its diet, and the soil substrates and geology of the bedrock in its habitat range (Gannes et al., 1998). These effects cause differences in the (p. 210) isotopic composition of the tissue, which can then be analysed after the animal has died. It is in this way that isotope analysis of modern and historic animals can be used as a method for reconstructing the diet, climate, and habitat of the animal while it lived (Koch et al., 1994).
But what exactly is an isotope? An isotope is a naturally occurring form of an element that varies in its atomic mass due to its number of neutrons. This variation in mass causes isotopes of elements to react differently in chemical reactions, meaning that living organisms incorporate varying amounts of each isotope and metabolize them differently (DeNiro and Epstein, 1978; Sharp, 2007). This is called fractionation, and is one of the most fundamental aspects of measuring isotope ratios in animal tissue, because it is imperative to understand how the isotopes of specific elements travel from the biosphere into the tissue of the animal being analysed so that the animal’s diet and habitat are understood. These isotopic ratios are measured by a mass spectrometer, so the resulting value is actually a ratio of the heavy to light isotope relative to a standard. For example, carbon isotope values are expressed with reference to 13C (the heavier isotope) compared to 12C (the lighter isotope), and are written δ13C to denote this ratio (Sharp, 2007).
This chapter focuses on stable isotopes, which are naturally occurring and do not undergo decay, and the various stable isotopes of an element behave similarly both chemically and physically (Gannes et al., 1998). Analyses of stable isotopes are most commonly used in ecological studies because they reflect aspects of the animal’s diet and habitat that are useful for understanding animal ecology. The next section will present case studies in which the technique has been utilized to understand the diets of African elephants in the past for the conservation of modern elephant populations, and how these data could be further integrated alongside modern isotope studies of elephants in the future.
Elephants in the Wildlife Conservation Policy Landscape
The increasing demand and exploitation of African elephant ivory on a global scale peaked in the late nineteenth century, when the value and use of ivory changed from being an enigmatic and valuable commodity to a raw material used as the Victorian version of modern plastic (Beachey, 1967; Sheriff, 1987). Yet it was not until poaching became large-scale, conducted by professional hunters who moved tonnes of ivory in the mid-twentieth century that there was an internationally recognized impetus to protect extant elephant populations (Parker, 1979). The growing concern raised by governments and conservation groups over how to control these poaching operations provided a catalyst for the protection of African elephants at an international level. The Convention on International Trade in Endangered Species (CITES) listed the African elephant as an endangered species in 1976, then revised its status in 1989, which offered elephants the highest amount of protection (Blanc et al., 2007).
(p. 211) International agreements controlling the trade in endangered wildlife, therefore, are often implemented to stimulate an immediate and effective impact for the protection of the species. However, they can lack long-term data on how species utilize the landscape over time. For example, understanding the feeding behaviour and migration of elephant populations prior to the gazetting of national reserves helps to understand where wildlife corridors and watering holes need to be protected and managed to control populations moving outside of national park boundaries (Croze and Moss, 2011). One of the problems comes in collecting historic data. Extracting relevant information from data sets on animal populations that span different regions and time periods is not simple, especially for elephant conservation as a continent-wide phenomenon. Thus, important decisions affecting elephant protection and changes to these policies are often made without a thorough understanding of how elephant populations have historically responded to and rebounded from periods of intense exploitation and/or habitat modification (Gillson and Lindsay, 2003; Milner-Gulland and Beddington, 1993). This lack of historic data is particularly relevant in the current climate of conservation agendas being renewed, elephant poaching on the rise, and many African governments arguing that international conservation agendas set by CITES give little attention to the economic constraints of managing elephant populations and stockpiles of ivory (Blignaut et al., 2008; Wittemyer et al., 2014).
While there have been an impressive number of studies investigating modern elephant populations across Africa, most of these studies have focused on population numbers, migration, and the immediate impacts of elephants on local vegetation and biodiversity (e.g. Codron et al., 2006; De Boer et al., 2013; O’Connor et al., 2007; Scheiter and Higgins, 2012). Thus, there is a lack of long-term data and a historical understanding of the demographics, movement, and feeding behaviour of elephants in these same landscapes in the past, though this has begun to be recently addressed (e.g. Clegg, 2008; Codron et al., 2012; Coutu, 2011; Croze and Moss, 2011; Ntumi et al., 2009). Because they are a keystone species, their survival and population size maintains the balance of the ecosystem; in other words, many plants and animals depend on the existence of the elephant to thrive (Mills et al., 1993). For example, forest elephants are frugivores (fruit consumers) and are known to increase tree diversity by distributing seeds in their dung across their habitats (Campos-Arceiz and Blake, 2011). Thus, they are arguably an important species to understand in the context of their impact on the historical ecology of African landscapes in the past. This has direct implications for modern conservation if the research on past populations is conducted in a way that is applied and practical. Addressing this point, Gillson and Lindsay (2003) proposed that a better way to tackle the current disassociation in elephant management between broad, economically-driven conservation decisions and local, ecologically-driven conservation ones is to understand the historic impacts of the ivory trade on local elephant populations in specific landscapes. There is a reliance on short-term data sets, especially observational data, which is immediate and relevant to short-term management decisions but does not offer a long-term perspective. Historical data sets regarding the behaviour of elephant populations are more difficult to interpret due to their fragmentary (p. 212) nature, though this type of data is something which palaeoecologists and archaeologists are trained to analyse. The remainder of this chapter will focus on case studies from eastern and southern Africa which have successfully attempted to bridge these knowledge gaps by creating historic data sets for African elephant populations.
Why is Knowing Historic Elephant Diet Important?
A significant debate in the management of African elephant populations in savannah ecosystems is the extent to which elephants impact the landscape through their feeding preferences and large daily vegetation requirements (150 kg of biomass/35 trees foraged per day; Scheiter and Higgins, 2012; Shannon et al., 2008). This debate is of specific concern as an overpopulation of elephants in restricted areas such as national parks can change the vegetation cover of a habitat dramatically within a period of decades (Scheiter and Higgins, 2012). This occurs due to elephants clearing paths and consuming/knocking down trees, which destroys woodland and can eventually lead to an opening of the landscape and thus a change in the distribution of woody vegetation cover (Dublin et al., 1990; Owen-Smith et al., 2006). Historically, the reverse scenario is often cited by archaeologists and historians as one of the impacts that the increased demand for ivory had on African habitats in the nineteenth and early twentieth centuries (Håkansson, 2004; Thorbahn, 1979). If the ivory trade caused a disproportionate reduction of elephants in certain regions, this would have subsequently increased dense vegetation cover in these habitats caused by the reduced pressure on woodland as a key source of elephant diet. After elephants were intensively hunted out of certain habitats, these areas would have likely become dominated by woody scrub and bush, and this change would have certainly had further impacts on the biodiversity of those habitats for the sustainability of other species (Nasseri et al., 2011; Ogada et al., 2008), but also on human habitation due to the creation of an open landscape suitable for agriculture or pastoralism (Håkansson, 2004).
There is evidence to suggest, however, that the elephant/vegetation dynamic is much more complex. For example, studies in southern Africa have demonstrated that the existence of large elephant herds is not always consistent with the destruction of woody vegetation cover (Kalwij et al., 2010). This would support the assumption that historically, when the roaming patterns of savannah elephants were less restricted, they seasonally selected mosaics of vegetation. Events from the nineteenth century onwards, nevertheless, may well have had an impact on their vegetation preference by causing elephants to rely more consistently on woodland resources for longer periods. For example, with reference to southern Zimbabwe, Clegg (2008) argues that woodland loss has been a long-term phenomenon that was initially caused by the ivory trade because elephants were forced into woodlands for protection against hunters. This led to an over-exploitation of woodland once elephant numbers increased in the mid-twentieth century and was further compounded by the decrease in both grassland and woodland (p. 213) habitats near permanent water sources due to expanding human settlement, agriculture, and the creation of national parks.
Thus, if it were possible to establish the extent to which elephants consumed woody vegetation before the intensification of the ivory trade, this would help to evaluate how much habitat modification could be attributed to changing elephant distribution patterns during intense periods of elephant hunting in the past.
Isotope Analysis as a Window on Historic Elephant Diet
Fortunately, isotope analysis allows us a window into understanding historic elephant diet, as the stable carbon isotope ratios measured in historic elephant tissue are an indication of the type of vegetation they consumed when the tissue was growing. In African habitats, the C3 photosynthetic pathway is the standard way in which plants such as trees, shrubs, and herbs take in CO2 from the air and transform it into sugars which provide the energy necessary for growth. The C4 photosynthetic pathway is the way in which most tropical grasses have evolved and adapted to thrive in hotter climates, so they use a different mechanism to photosynthesize in order to capture CO2 to the fullest efficiency (van der Merwe et al., 1988). The difference in these two types of photosynthesis is thus measured by carbon isotope analysis so that C3 vegetation has δ13C values between –25 and –29‰, while the range for C4 plants is between –11 and –14‰ (Cerling et al., 1999, 2009). African elephants are mixed feeding herbivores which rely on a diet of different plant species, from trees and shrubs to tropical grasses, and therefore the δ13C values of individual elephants can range widely (Tieszen et al., 1989).
The nitrogen isotope ratios measured within elephant tissue also reflect vegetation in the diet. Nitrogen is influenced by the aridity of the habitat due to the effect of water stress and nitrogen recycling in the soil in which the vegetation grows (Aranibar et al., 2008; Murphy and Bowman, 2009). Because of this, the δ15N values of vegetation recorded in arid African environments are typically high. For example, Ishibashi et al. (1999), van der Merwe et al. (1990), and Coutu (2011) measured high δ15N values (12.4‰, 13‰, 12‰) in the tissues of elephants from arid environments (Ethiopia, Namibia, Somalia). Carbon and nitrogen isotope ratios measured in elephant tissue therefore provide a window to historic elephant diet and the habitat in which that elephant lived.
Measuring Historic Elephant Diet in Southern and Eastern Africa during the Nineteenth and Twentieth Centuries
The most extensive studies on historic elephant diet patterns have been conducted in Kruger National Park (KNP), South Africa (Codron et al., 2006, 2011, 2012). By sampling the tusks of 14 elephants for isotope analysis, it was possible to reconstruct diet (p. 214) histories of individuals on a seasonal basis between 1903 and 1993, making it the longest and most-detailed dietary study on any extant species. Because tusks grow by accretion and throughout the life of the animal, it is possible to analyse the growth of the tusk in cross-section, as the growth layers form concentric rings, much like tree rings (Codron et al., 2012). Codron et al. (2012) radiocarbon-dated these growth layers to establish a chronology for the isotope values measured in each of these rings and as a proxy for measuring variations in time-sensitive environmental indicators such as temperature, rainfall, and vegetation cover in KNP over time (see also Ekblom, Chapter 5). It was thus possible to gather multi-decadal isotopic information from tusks sampled incrementally due to the long lifespan of elephants (some up to 60 years). One of the aims of the study was to measure individual diet histories using carbon and nitrogen isotope analysis to determine if climate change or park management decisions had an effect on the dietary preferences of the elephants. The years under study (1903–1993) were particularly important due to the significant changes in the management of the KNP landscape, including the decline in woody vegetation cover and culling of elephants in the park from 1967 to 1999 (du Toit et al., 2003; Freeman et al., 2009).
In the tusks analysed from KNP, Codron et al. (2012) found a consistent pattern in the carbon isotope values suggesting that the elephants were mixed feeding on graze and browse, even during years of well-documented fluctuations of vegetation change. As such, the isotope values of the tusks did not correlate to climate records indicating significant shifts in rainfall and temperature during the years the tusks were growing. Codron et al. did observe a general increase in the amount of C4 that Kruger elephants consumed throughout the twentieth century, especially in the wet seasons, which relates to a shift in vegetation cover more recently in the park being dominated by grassland (Fig. 11.2; Owen-Smith et al., 2006). With this substantial data set of 14 individuals on a seasonal basis for over 50 years, they argued that the long-term trends showed that elephants are ‘dietary generalists’ and that their large body mass necessitates the ability to switch between browse and graze over long time frames (Codron et al., 2012). They further suggested that the ability of elephants to respond to changes in vegetation availability in their habitats caused either by natural or man-made factors could be one of the reasons why elephants have survived long-term ecological changes in their habitats in the past. This led the authors to conclude that elephants will have a unique dietary ability to survive future human or climate engendered habitat change.
The dietary history of elephants has also been analysed in Amboseli and Tsavo National Parks, Kenya, where elephants consume the highest amount of C4 grass in their diet compared to other populations across Africa (van der Merwe et al., 1988). Fig. 11.3 is a compilation of the carbon isotope results from elephant populations in these two national parks for the past 40 years. One particular study, Koch et al. (1995), found an increasing trend in the amount of C4 vegetation in the diet of Amboseli elephants in recent decades. They were particularly interested in this trend as it correlated to the end of a drought which occurred in the region in the late 1970s. They argued that this drought would have influenced the dietary preferences of Amboseli elephants, as elephants would have had to migrate outside of the park to surrounding woodlands for (p. 215) food. This dietary adaptation is visible in the carbon isotope ratios measured in the tissues of elephants which lived during and after the drought (Fig. 11.3). Populations that were alive during the drought exploited more C3 resources (δ13C values between –25 and –22), whilst populations alive after the drought, when increased rainfall brought an increase in the availability of C4 grass, subsequently exploited more C4 inside the park (δ13C values between –21 and –17).
This pattern also exists in the carbon isotope results published for elephants living in Tsavo National Park (in the same region of south-eastern Kenya) during the drought (Fig. 11.3). However, the most recent values published for elephants in Tsavo and Amboseli by Cerling et al. (1999, 2007) suggest that elephants in both parks are returning to mixed feeding on graze and browse. Because these data sets are from different publications and the time scales are more dispersed than the Codron et al. (2012) study on directly dated tusks from individual elephants, it is difficult to draw specific conclusions about the effects of climate, management, and vegetation change in Amboseli and Tsavo over the past 40 years. But there is a general trend that climate and vegetation availability played a role in elephant feeding behaviour and that elephants responded to these changes by adapting their diet. There is also a consistent trend in all of these studies that modern elephants in savannah habitats are increasingly exploiting C4 vegetation, specifically in the rainy seasons when it is more readily available, palatable, and nutritional (Cerling et al., 2009; Codron et al., 2011). But how much this is a (p. 216) recent phenomenon of elephant behaviour being constrained in protected areas, and how much this is due to the flexibility of an elephant selecting its vegetation is difficult to conclude without understanding the dietary histories of elephants in landscapes prior to the establishment of these boundaries.
Recently, some research attention has been given to the analysis of elephant tissues from big game hunting collections formed by hunters and colonial travellers to eastern Africa during the late nineteenth and early twentieth centuries (Coutu, 2011, 2015). The unique aspect of sampling material from these collections is that there is a precise record of when and where the elephant was shot, making it possible to build individual life histories of the elephant skeletons through archival photographs and written records, but also through isotope analysis of the preserved elephant tissue (Coutu, 2015). For example, incremental isotope analysis of the tail hairs preserved in these collections allows for direct comparison with studies by Codron et al. (2013) and Cerling et al. (2009) which analysed tail hairs of South African and Kenyan elephants. Because the date of death is recorded for the historic tail hairs, it is possible to build a well-dated snapshot of individual elephant diet in a specific landscape in the past.
The three historic elephant tail hairs in Fig. 11.4 represent elephants from different habitat zones of eastern Africa including an arid savannah with low rainfall and dominated by C4 vegetation, a mixed savannah with fluctuations in C3 and C4 vegetation and rainfall patterns seasonally, and a closed-canopy forest environment, which is humid and dominated by C3 vegetation. Therefore, the distinct vegetation and climates of these (p. 217) (p. 218) habitats cause differences in the carbon and nitrogen isotope compositions of elephants living there. Isotope analyses combined with documentary evidence from the big game hunters about these landscapes provide a way to track the diet and habitat type that these historic elephants lived in over a century ago.
In Fig. 11.4, there are significant fluctuations in both the δ15N and δ13C values along the tail hair of the Ogaden elephant, and, compared to the other two elephants, these values are higher. These values indicate that this elephant exploited a range of different vegetation types, though a substantial amount of C4, during the time that its tail hair was growing, which is estimated as a period of approximately 1.5 years (Coutu, 2011). High δ15N and δ13C values are typically measured in modern elephants which live in open, arid C4 grassland habitats (van der Merwe et al., 1990). Therefore, the pattern seen in the Ogaden elephant is an indication that the habitat in which this elephant lived in 1896 was likely similar. This evidence is corroborated with Powell-Cotton’s (1896) diary entries from the days surrounding this elephant’s death, in which he describes an open, grassy landscape on travel by camel. Furthermore, the projected historic climate records for this area indicate that it received less than 300 mm of rainfall that year (Jones and Harris, 2008). Elephants in more humid, closed-canopy forests, on the other hand, live in habitats that are not affected by strong seasonal shifts in rainfall and vegetation which occur in savannah ecosystems (Cerling et al., 2004). Thus, the isotope ratios measured in the tissue of these elephants do not fluctuate as much throughout the year. Furthermore, because of the abundance of C3 vegetation, and due to the canopy effect of carbon recycling in rainforests, they also have more negative δ13C values compared to savannah elephants (Cerling et al., 2004). In Fig. 11.4, this is illustrated by the historic elephant from Makala, which has stable δ13C and δ15N values measured along the entire length of the tail hair, a period of at least one year. This elephant also has the most negative δ13C values of the three elephants measured, which indicates that it consumed C3 vegetation year-round. Powell-Cotton describes shooting this elephant in thick, thorny bush and that the vegetation was dense, with animals only visible at waterholes and clearings in the forest (Powell-Cotton, 1906). The Mt Elgon elephant has the lowest δ15N values and δ13C values ranging between the other two elephants, which indicate that this elephant consumed a mixture of C3 and C4 vegetation, with the fluctuations seen along its tail hair indicative of seasonal fluctuations in vegetation available in its habitat. Mt Elgon is an extinct volcano dominated by C3 vegetation in the upper altitudes of the mountain and C4 grass on the plains below (Coutu, 2015; Simonetti and Bell, 1995). Thus, the isotope values in the tail hair indicate that this elephant exploited both of these resources, which is typical of elephants in montane regions (Afolayan, 1975).
Studies on modern elephant tail hair (Cerling et al., 2004, 2009) have shown that there is a delay between when the vegetation is consumed and the synthesis of the elements such as carbon and nitrogen into the growth of the tail hair. Cerling et al. (2009) found that short-term bursts of C4 consumption were not always reflected at a 1 cm (18 day) scale of hair growth because the long-term pool of hair synthesis reflects the primary diet of the individual (Cerling et al., 2009). This would mean, then, that the historic elephants in Fig. 11.4 that have significant fluctuations in the isotope values in their (p. 219) tail hairs would have experienced a shift in diet (between rainy and dry seasons, for example) for long enough to be measured in the hair.
Coutu (2011) found that overall, including the tail hairs of other elephants from East Africa in addition to the three featured in Fig. 11.4, isotope analysis of historic savannah elephant hair revealed significant fluctuations in the δ13C and δ15N values measured along the tail hair, indicating that these historic elephants exploited both C3 and C4 vegetation and that this preference fluctuated seasonally. This pattern fits with the hypothesis put forward by recent studies (Clegg, 2008; Loarie et al., 2009) which suggest that historically, savannah elephants were able to roam more widely and select vegetation preferences based on what was most palatable and available at different times of the year. These results also concur with the studies detailed earlier in this chapter from historic elephants in eastern and southern Africa, particularly the idea proposed by Codron et al. (2012) that elephants are ‘dietary generalists’ and that this mixed feeding pattern and non-reliance on a specific vegetation niche has allowed them to be successful in the face of vegetation change and habitat modification engendered by humans and/or climate. Thus, the combination of the isotopic information preserved in the tail hairs with the archival information provided by the hunting accounts and historic climate records makes these historic skeletons unique and relevant for understanding historic elephant diet. The question that remains is how to make the histories of individual elephants relevant and applicable for understanding the current relationship between elephants, humans, and the habitats in which they coexist.
Mapping Elephant Isotope Data in the Past, Present, and Future
The overall conclusion of these case studies suggests that savannah elephants are inclined to select different types of vegetation based on changes in seasonal climate and vegetation palatability with little regard for landscape boundaries (Cerling et al., 2009). This supports the argument that homogeneous vegetation zones present in national parks today cause elephants to roam outside park boundaries, which can cause management problems and over-exploitation of specific resources (Scheiter and Higgins, 2012). Mapping diet histories by using detailed isotope analysis of historic elephants coupled with palaeoecological data and modern elephant isotope data would allow for an understanding of how the relationship between vegetation, diet, and elephant movement has changed over time in a specific landscape. These data could contribute to management decisions regarding elephant migration, as elephants are capable of moving great distances to access specific vegetation patches (Codron et al., 2011; Loarie et al., 2009). This could also be particularly useful for the management of wildlife corridors in order to protect wildlife from death due to roads (Newmark et al., 1996), but also in protecting human settlements from damage and danger caused by wildlife (Goldman, 2003). One (p. 220) example of this was the proposed international highway through Serengeti National Park, Tanzania, which was opposed within the international conservation community due to the disruption of wildlife corridors and wildlife habitats that a major highway would cause (Dobson et al., 2010). Managing these landscapes in the face of these competing interests is therefore a constant challenge.
Another challenge that comes with evaluating historic trends in elephant populations is the lack of resolution when matching local climate data for a particular region with detailed dietary patterns for elephants in a specific habitat over time. One way to address this problem in the future is to incorporate high resolution palaeoecological data for a specific landscape with isotope data of historic elephants in these same locations. The key to making this leap with the historic data relies on the amount of integration that occurs between historical ecology approaches, historic data sets, and modern forms of management and conservation in these same landscapes (Brewer et al., 2012; Gillson and Marchant, 2014; Rick and Lockwood, 2013). One way of bridging these gaps is to utilize new platforms and technology for bringing this data together. For example, with mapping tools and online databases managed through open source platforms such as AfricaMap (<http://worldmap.harvard.edu/africamap/>) and IsoMap (<http://isomap.org>), it is possible to layer historical data with modern data in a spatial way. For example, Coutu (2011) created maps for East Africa that amalgamated historic elephant isotope data with historic climate records, vegetation, and geological data. Integrating this data in a visual way can aid in evaluating trends in the data sets. In this way, Geographic Information Systems are useful at connecting the relationship between the geographical distribution of isotope values with corresponding climate data in a region, which would be particularly relevant for the integration of historical data sets with modern ecology, as this data can be layered and trends analysed simultaneously in this platform.
Another way to utilize spatial data is to redress the imbalance of research on African elephants by region. Although elephants in central Africa are listed as most vulnerable in the International Union for the Conservation of Nature (IUCN) Red List, these are also the populations that are the least researched, especially for historic populations (Campos-Arceiz and Blake, 2011; Maisels et al., 2013). A dense proportion of elephant populations exist in countries that have experienced recent war and ongoing conflict, such as the Democratic Republic of the Congo and the Republic of South Sudan. These conflicts remain the foremost reason for the lack of data on these elephant populations, but these regions are important areas for elephant conservation as a result, and many of these same areas were also historically significant elephant hunting grounds. Much of the ivory exported from the East African coast in the nineteenth century was sourced from the Congo region, for example (Beachey, 1967; Coutu, 2011; Håkansson, 2004). Therefore, these regions could be important places to investigate the links between historic and modern elephant populations. If research agendas in both disciplines can be aligned and data sets more freely available and integrative, it is possible to begin targeting areas of research in a much more coherent and holistic way (Stephenson and Ntiamoa-Baidu, 2010).
(p. 221) Conclusion
With a better understanding of the dietary patterns of historic elephants and the historical ecology of habitats where elephants still exist, it is possible to make more informed decisions about managing their modern distribution in protected areas. The case studies in this chapter highlight the ways in which the technique of isotope analysis as applied to historic populations can be useful to wildlife conservation if targeted data sets within national parks or specific landscapes are applied. However, it is important to note that isotope data cannot exist in isolation, but rather, must be viewed within the context of other information such as archaeozoological (Lyman, Chapter 10), archaeobotanical (Ekblom, Chapter 5; Minnis, Chapter 2), and genetic data. The correlation of these data sets can provide important information about the dynamics not only of the individual and its palaeodiet as provided by isotope data, but also about the interaction of that individual with other animals and humans, especially in time periods when the landscape was less intensively utilized and managed.
Though this chapter focused on the African elephant, there have been a number of important studies within historic isotope ecology that have contributed to the understanding of other species in different places and times, such as the sea otter in British Columbia (Szpak et al., 2012), the Pacific fur seal (Moss et al., 2006), and the distribution of fish in the North Sea (Jennings et al., 2002). To support the other voices in this volume, historical ecology and the knowledge gained by palaeoecologists, historians, and archaeologists working with historical data sets can play a key role in conservation by contributing knowledge about historic relationships between animals, humans, and their surrounding ecosystems.
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