CURRENT ECOSYSTEMS AND HISTORY

That current patterns and processes in nature have a historical trajectory was realized already in the theory of evolution. In palaeoecology, to take another example, pollen analysts have been working on the history of long-term changes in vegetation for almost a century (Boyd & Hall Reference Boyd and Hall1998). Such approaches, however, were somewhat ahistorical (as perceived by a historian) for two reasons. On the one hand, they regarded the past as essentially predictable (see for example how originally biostratigraphical zones [Boreal, Atlantic] became chronostratigraphical zones in common scientific language). On the other hand, they often disregarded human activity (with the exception of domestication, of course) (for a recent attempt at a more historical approach in evolutionary ecology, see Brooks Reference Brooks1985; Brooks & McLennan Reference Brooks and McLennan1999). A significant change in this attitude happened about half a century ago, when a larger number of scientists started to appreciate the profound human impact on practically every landscape in the world (Birks et al. Reference Birks, Birks, Kaland and Moe1988). Initially this meant that patterns and processes that had been understood as natural were given a new, anthropogenic aspect: humans were accepted as an ecological factor. This, however, still often (although by no means always) implied that people were outside the system, that they disturbed processes that otherwise had a predictable trajectory (Cronon Reference Cronon1993; Russell Reference Russell1997).

The next key argument in the process of integrating ecology and history was that human activity was not an outside factor that fitted awkwardly into natural processes, but rather an organic part of such processes, or, in other words, that nature and culture are impossible to tell apart (McDonnell & Pickett Reference McDonnell and Pickett1993a; Haila Reference Haila1999, Reference Haila2000). As a result, it is increasingly difficult to define what a ‘natural’ ecosystem might be. Woodland ecologists, for example, demonstrated that past land-use, continuity and management history influence the vegetation of individual woods to the extent that anthropogenic impact becomes an integral part of vegetation development. This, apparently, has two main reasons. First, things that happened in what would be considered the distant (and therefore irrelevant) past by modern ecologists have a decisive effect on seemingly natural patterns. For example, past land-use influences soil conditions and vegetation composition through long time spans (Sandor et al. Reference Sandor, Gersper and Hawley1990; Verheyen et al. Reference Verheyen, Bossuyt, Hermy and Tack1999; Hermy & Verheyen Reference Hermy and Verheyen2007), extending as far back as the Roman Period (1st–4th centuries AD) in several French woods (Dupouey et al. Reference Dupouey, Dambrine, Laffite and Moares2002; Dambrine et al. Reference Dambrine, Dupouey, Laüt, Humbert, Thinon, Beaufils and Richard2007; Plue et al. Reference Plue, Hermy, Verheyen, Thuillier, Saguez and Decocq2008). Similar studies also abound for other types of vegetation, such as grasslands (Pärtel et al. Reference Pärtel, Mändla and Zobel1999; Eriksson et al. Reference Eriksson, Cousins and Bruun2002; Herben et al. Reference Herben, Münzbergová, Mildén, Ehrlén, Cousins and Eriksson2006). Second, as Rackham (Reference Rackham2003, Reference Rackham2006) argued, certain conditions created by human impact have existed for such a long time that they are incorporated into the ecology of current woods. To take an example, fragmentation, which is usually viewed negatively by conservationists (for example Saunders et al. Reference Saunders, Hobbs and Margules1991), has in some protected woods existed for millennia and played an active part in shaping the current vegetation. Had these woods not stood in a fragmented landscape, they would have developed into different (and not necessarily richer) ecosystems from those valued so highly today (but see also Ewers & Didham Reference Ewers and Didham2006). A more comprehensive view on this issue is that ecosystems are highly complex (for example Bradbury et al. Reference Bradbury, Green, Snoad, Bossomaier and Green2000; Newell & Wasson Reference Newell, Wasson, Castelein and Otte2002). Their properties and dynamics are determined by mutual constraints among the individual elements over time. This ‘refers simply to the fact that the local rules of interaction change as the system evolves and develops’ (Levin Reference Levin1998). Changes in one factor influence other factors, which, in turn, have their effect on the first factor and so on. The patterns of these feedback loops through time are difficult to map and, especially when humans are involved, are unpredictable.

Another major reason why historical information is essential in understanding present ecosystems was raised by the American ecologist D.R. Foster (Reference Foster2000). He argued that because ‘time-lags develop in the response of all biological and physical systems to disturbance or environmental change’, instantaneous measurements often collect data about events and processes that without a historical insight remain hidden from the investigators (see also Newell & Wasson Reference Newell, Wasson, Castelein and Otte2002; Newell et al. Reference Newell, Crumley, Hassan, Lambin, Pahl-Wostl, Underdal and Wasson2005; Jackson et al. Reference Jackson, Betancourt, Booth and Gray2009). Repeated, longer-term observations may provide a solution, but only if they explicitly include historical events as explanatory data.

In addition, history also informs about the ‘invisible’ parts of ecosystems (Clark Reference Clark1990; Foster et al. Reference Foster, Orwig and McLachlan1996; Foster Reference Foster2000). There are some, typically catastrophic, disturbance events which are important elements of current ecosystems but will certainly not occur during a three-year grant project and may not occur for hundreds of years. The effects of extreme floods, fires or storms, if luck fails to bring them around, can only be approached through historical studies. A good example is the ‘Great Storm’ of 1987 in England, a powerful reminder of a forgotten ecological factor in that country (Kirby & Buckley Reference Kirby and Buckley1994; Rackham Reference Rackham2003).

In connection with the previous issues, the general topic of change and dynamism in ecosystems has also been fostered by a historical approach. The lesson history teaches is that ‘perhaps the most natural feature of the world in which we find ourselves is its continual flux’ (Jackson & Hobbs Reference Jackson and Hobbs2009). Ecosystems change on many temporal scales from days to millennia, therefore current systems should be seen as necessarily temporal elements in a process that can have a multitude of realizations (Bowman Reference Bowman2001; Jackson Reference Jackson2006). Any given ecosystem can be part of a number of such processes: the mostly lodgepole pine (Pinus contorta) forests in Yellowstone National Park, for example, experience cycles of smaller fires and regrowth at relatively regular intervals. To this are added the effects of occasional huge fires and storms (Romme & Despain Reference Romme and Despain1989). At the same time, these forests represent one phase in the general vegetation development since the latest Ice age (Whitlock & Bartlein Reference Whitlock and Bartlein1993). Historical knowledge not only allows researchers to understand these processes, but also provides an opportunity to identify keystone processes, those that are apparently the most important in the given ecosystem (Marcucci Reference Marcucci2000).

ECOLOGICAL CONSERVATION, MANAGEMENT AND HISTORY

Most theoretical research into the significance of history for ecosystems focused on conservation and restoration. This is by no means accidental. Restoration ecology, if it is to take itself seriously, must, by definition (the Latin prefix re- implies going back to or repeating a previous stage), be concerned with the past. Consequently, some scholars called restoration ecology ‘applied historical ecology’ (Swetnam et al. Reference Swetnam, Allen and Betancourt1999; Rackham Reference Rackham2003; Balée Reference Balée2006). Solid theoretical foundations are especially needed in this field, because management decisions will inevitably influence landscapes. These decisions cannot be avoided: doing nothing is also a form of management with its own distinct consequences.

On a basic level, historical ecology is thought to be able to identify baseline conditions (typically those before significant human impact) that can serve as restoration targets (Egan & Howell Reference Egan, Howell, Egan and Howell2001; Swetnam et al. Reference Swetnam, Allen and Betancourt1999; Balée Reference Balée2006; Fule et al. Reference Fule, Covington and Moore1997). This research direction has been particularly strong in North America and Australia, where pre-European settlement conditions were often interpreted as natural. However, many studies pointed out that this view could be misleading for two main reasons (see for example Pickett & Parker Reference Pickett and Parker1994; Landres et al. Reference Landres, Morgan and Swanson1999; Lentz Reference Lentz2000; de Vries Reference de Vries2005). First, history did not start with European settlement. Native peoples had a large influence on many landscapes. This influence is now recognized to the extent that in recent years criticism was voiced (Vale Reference Vale1998, Reference Vale2002) that we should not swing to the other extreme and view all pre-European settlement North American landscapes as largely modified by humans. In Europe, however, this issue is less discussed. Although early 20th-century historical geographers had a tendency to overemphasize the landscape impact of their own nation, environmental archaeology is a flourishing and well-recognized subject, and the American concept of ‘wilderness’ (Nash Reference Nash1967; Oelschlaeger Reference Oelschlaeger1991) is very hard to interpret in a European context. It is for certain that practically all European landscapes have been heavily influenced by humans for thousands of years (Birks et al. Reference Birks, Birks, Kaland and Moe1988), and that ‘natural’ conditions, if they are to be found at all, have to be searched for somewhere in or before the Mesolithic (Szabó Reference Szabó2009). The second problem with defining baseline conditions stems from the realization, discussed above, that ecosystems are not static, but are in constant flux. Consequently, selecting a particular temporal phase as the most desirable target is often rather difficult to justify.

A much more useful concept than baseline conditions is that of the ‘historical range of variability’ (Morgan et al. Reference Morgan, Aplet, Haufler, Humphries, Moore and Wilson1994; Rackham Reference Rackham and Sutherland1998; Aplet & Keeton Reference Aplet, Keeton, Baydack, Campa and Haufler1999; Hessburg et al. Reference Hessburg, Smith and Salter1999; Landres et al. Reference Landres, Morgan and Swanson1999; Keane et al. Reference Keane, Hessburg, Landres and Swanson2009; Mitchell & Duncan Reference Mitchell and Duncan2009; Thompson et al. Reference Thompson, Duncan and Johnson2009). Introduced in the 1990s, this concept, rather than focusing on a single state, includes the full variation of conditions that are known to have occurred in history. Current conditions and processes are evaluated against this background. This idea resolved the integration of dynamism into ecosystem management. Change is considered to be acceptable as long as it falls within the historical range. What is more, with a shift from patterns to processes, dynamic systems became conservation targets themselves (Foster et al. Reference Foster, Orwig and McLachlan1996; Jackson & Hobbs Reference Jackson and Hobbs2009). Rivers are good examples of such systems. It is understood that the quickly changing meanders of any larger river in some moment in history cannot be a restoration target. The whole system of the flood plain needs to be restored, where floods, geomorphology, climate, vegetation and traditional fishing, amongst others, together create a dynamic landscape. Another perspective on this issue is that the historical range of variability concept helps to ‘isolate the unconservable’: to identify things that are inherently ephemeral (Rackham Reference Rackham1994). These include not only passing phases in a dynamic system (such as the meanders above) but also phenomena that are not part of the long-term history of a site (such as a poplar plantation on the flood plain). A historic view on dynamic ecosystems also allows for a better understanding of change itself in all its temporal and spatial variation. An especially important issue here is that of driving forces, which often create considerable challenges (Brandt et al. Reference Brandt, Primdahl, Reenberg, Krönert, Baudry, Bowler and Reenberg1999; Bürgi et al. Reference Bürgi, Hersperger and Schneeberger2004). A typical example is global climate change. From historical and palaeoecological records it is known that neither the current extent nor the current speed of change are necessarily unprecedented, and they therefore may fall within the historical range of variability. Such change, however, when caused by human activities, is (as far as can be told) exceptional and has no historical parallels (McNeill Reference McNeill2000). Historical ecology offers an integrated understanding of change that considers causalities as well as sequences of events (Christensen Reference Christensen1989; Bürgi & Schuler Reference Bürgi and Schuler2003; Bürgi et al. Reference Bürgi, Hersperger and Schneeberger2004; Szabó Reference Szabó2010).

In addition to enhancing knowledge about managed ecosystems, a historical perspective also sheds light on the process of management itself. Historical ecology studies not only past ecosystems but also past ecosystem management. The effects of past management systems can provide an indication of how current ecosystems may react to management efforts. By the same token, present management should be seen as part of an on-going ‘experiment’ with ecosystems, rather than a process with a confidently predictable outcome (Harper Reference Harper, Jordan III, Gilpin and Aber1987; Newell & Wasson Reference Newell, Wasson, Castelein and Otte2002; Thompson et al. Reference Thompson, Duncan and Johnson2009). History provides an opportunity to assess policy making and management as an adaptive process (Newell et al. Reference Newell, Crumley, Hassan, Lambin, Pahl-Wostl, Underdal and Wasson2005). Or, as historians would say it, only ‘those who cannot remember the past are condemned to repeat it’ (Santayana Reference Santayana1906), which in this case means repeating failures of past conservation efforts. It is especially important that natural resource management be aware of its own history with its changing fashions. The past provides a standard against which to check the current wave of fashion (be it zero management, species extirpation or species reintroduction; Chase Reference Chase1986; Rackham Reference Rackham and Sutherland1998). The most important feature of this standard is that it is local: it warns not to accept conservation principles from other countries or continents uncritically (Marcucci Reference Marcucci2000). As argued by Foster et al. (Reference Foster, Swanson, Aber, Burke, Brokaw, Tilman and Knapp2003), perhaps the most critical contribution of historical knowledge to the process of ecological conservation is that it reinforces ‘the conviction that, although science and history may inform management, the ultimate driver of policy is human values and perceptions’, which is especially important to keep in mind when confirming or negating the rights of various groups of people to participate in management decisions (Hayashida Reference Hayashida2005). This, however, does not mean that conservation and restoration have no claim on objectivity. By embracing a human perspective, historical knowledge simply helps us to realise our own limitations and motivations.

A significant and somewhat undervalued way historical ecology helps conservation and management is that it emphasizes the uniqueness of every site (Rackham Reference Rackham and Sutherland1998, Reference Rackham2003). History, as a science, inherently focuses on individual places and events. Generalizations are arrived at almost exclusively inductively. Historical studies explain why a given site is special, why it is different from any other site in the world. It should be a priority in every management plan to perpetuate this genius loci, rather than making the site conform to what is thought to be the right state of that ecosystem by the present level of knowledge. Quite often this may entail preserving features that seem anomalous; the knowledge of history can provide the courage to accept the fact that our understanding of how the ecosystem in question works may be inaccurate or inadequate.

AN INTERDISCIPLINARY VIEW

Scientists often emphasize the importance of interdisciplinary efforts in order to achieve a deeper understanding of ecosystems. In fact, historical ecological research was originally initiated not with the aim of providing useful knowledge for nature conservation, but rather as an interdisciplinary venture in which natural scientists and humanists both tried to exceed the limitations of their respective disciplines (Bilsky Reference Bilsky1980). Bridging the divide between the ‘two cultures’ (Snow Reference Snow1959) in scientific research has become an explicit aim of historical ecology (Ingerson Reference Ingerson and Crumley1994). This has two distinct advantages. First, the higher variety of sources of information, the more secure knowledge about the past (and therefore about the present) is: ‘independent data sets provide an important cross-check in building consensus among collaborators’ (Crumley Reference Crumley, Hornborg and Crumley2007). Second, interdisciplinary research produces synergetic results that, in optimal cases, are more than the simple sum of information gathered from individual disciplines.

By now some scholars take this standpoint for granted. Newell et al. (Reference Newell, Crumley, Hassan, Lambin, Pahl-Wostl, Underdal and Wasson2005) argued that ‘many researchers in the international community have taken up the integration challenge. For these workers the question is no longer why, but how and what, to integrate’ (see also Crumley Reference Crumley and Crumley1994, Reference Crumley and Balée1998, Reference Crumley, Hornborg and Crumley2007; Bürgi & Russell Reference Bürgi and Russell2001; Balée Reference Balée2006; Balée & Erickson Reference Balée, Erickson, Balée and Erickson2006). Egan and Howell (Reference Egan, Howell, Egan and Howell2001) added that it also helps historical ecologists to ‘locate themselves within the ‘complementary opposition’ of culture and nature’, providing them ‘with a sense of personal, professional and bioregional identity’. An interdisciplinary view on ecosystems is also useful in understanding ecological processes on a landscape scale (Landres et al. Reference Landres, Morgan and Swanson1999; de Blois et al. Reference de Blois, Domon and Bouchard2002; Lunt & Spooner Reference Lunt and Spooner2005). Landscape, as emphasized mostly by anthropologists (Balée Reference Balée2006; Crumley Reference Crumley, Hornborg and Crumley2007), is one of the key concepts in historical ecology, because it provides a common platform for the investigation of the physical environment and human activity. This, however, poses its own interdisciplinary challenges. A common vocabulary is often not enough to create common understanding; in fact, the same words and expressions often have different meanings in various disciplines, which leads to confusion rather than cooperation (Wear Reference Wear1999). Furthermore, as pointed out by Meine (Reference Meine1999), ‘natural scientists and historians may gaze upon the same landscape, but they see different things and draw different lessons from what they see’. In order to succeed, scientists from various disciplines have to be able to ask common questions.

Lastly, historical ecological investigations are essential, because they link biological conservation to conservation in general (Rackham Reference Rackham and Sutherland1998). It becomes increasingly clear that the preservation of cultural heritage cannot be separated from the preservation of nature. Yet again, we are faced with the fact that nature and culture are indivisible, or, in David Lowenthal's words, ‘if they are twins, they are Siamese twins, separated only at high risk of the demise of both’ (Lowenthal Reference Lowenthal2005). Most of the world's landscapes are cultural landscapes, where ecologists, conservationists, historians, geographers, archaeologists and anthropologists must work together in order to understand at least some of the complexities of these landscapes. It must be realized that changing one part of a system (such as species composition, management system, settlement pattern or built heritage) inevitably influences all other parts.