You might be surprised by how much water it takes to grow and make our food. The food we eat makes up more than 2/3 of our total water footprint, mostly because of all the "virtual water" needed to produce that food. It seems pretty obvious when you really think about it; crops can’t grow without water. In the US, agriculture is responsible for 80 percent of all water consumed (water that is evaporated or otherwise removed from the watershed). Let’s take a look at a typical lunch. A loaf of bread requires about 240 gallons of water, and a pound of cheese takes about 382 gallons. So a simple cheese sandwich takes about 56 gallons of water. Throw in a small bag of potato chips at 12 gallons and you just ate about 68 gallons of water. Add some turkey and it jumps to 160 gallons! Thirsty? Rinse your sandwich down with an ice cold soda and you can add an extra 46 gallons of water onto your tab. The sheer amount of water used to make the food we eat every day can be mind-boggling.Let’s take a closer look at meat. Pound for pound, it has a much higher water footprint than vegetables, grains or beans. For instance, a single pound of beef takes, on average, 1,800 gallons of water. That huge water footprint is primarily due to the tremendous amount of water needed to grow the grass, forage and feed that a beef steer eats over its lifetime, plus water for drinking, cleaning and processing. In the US, at least 80 percent of beef cattle are "conventionally" raised. This means they eat grass in pasture, typically for 12 to 14 months, then they go to a feedlot for three to six months, where they eat feed made from corn and soy, because a grain-heavy diet speeds up the cattle’s growth. It takes about 147 gallons of water to produce one pound of corn, and a beef steer or heifer can eat 1,000 pounds or more of feed over a few months. All that grain and water really adds up! It also adds up for the average American who eats about 167 pounds of meat a year – three times the global average! By eating more vegetables, grains and beans and eating less meat, you can save water.Another important part of using water and other resources productively is to think about where our food comes from and how it is made. California produces more food than any other US state, supplying a large part of the country's milk, beef, produce and nuts. It is also one of the nation's driest states and is in the midst of an historic drought. As a result, California's agricultural sector puts enormous pressure on the water supplies of the entire southwest, often shipping those limited water resources overseas as food exports. Likewise, when we buy food that's been shipped from other states and countries, we're tapping into distant water supplies, too. Transporting food over long distances also requires large quantities of fuel that pollute the air, contribute to climate change and use a great volume of water. That's because it takes water to produce gasoline and other transportation fuels. In fact, it takes about 3/4 gallon of water to produce the gasoline needed to drive 1 mile. Diets that are made up of highly processed foods (like candy, chips and ready-made meals) also take a lot of water. Take, for example, the potato chip (as compared to a whole potato). After growing the potatoes – which takes the biggest portion of water – potato chip-processing takes additional water to clean potatoes and machinery, produce cooking oil for deep frying, produce the fuel for delivery, produce packaging, and so forth. The water use accumulates above and beyond what it would take to produce and eat a whole potato. In short, the more meat, dairy and processed foods we eat, the more water we consume. The next time you're thinking about what's for lunch, you might also want to appreciate how much water it took to make that meal. In the areas adjacent to the drowned Pleistocene continent of Sunda – present-day Mainland and Island SE Asia – the Austronesian Hypothesis of a diaspora of rice cultivators from Taiwan ∼4200 years ago has often been linked with the start of farming. Mounting evidence suggests that these developments should not be conflated and that alternative explanations should be considered, including indigenous inception of complex patterns of plant food production and early exchange of plants, animals, technology and genes. We review evidence for widespread forest disturbance in the Early Holocene which may accompany the beginnings of complex food-production. Although often insubstantial, evidence for incipient and developing management of rainforest vegetation and of developing complex relationships with plants is present, and early enough to suggest that during the Early to mid-Holocene this vast region was marked by different approaches to plant food production. The trajectory of the increasingly complex relationships between people and their food organisms was strongly locally contingent and in many cases did not result in the development of agricultural systems that were recognisable as such at the time of early European encounters. Diverse resource management economies in the Sunda and neighbouring regions appear to have accompanied rather than replaced a reliance on hunting and gathering. This, together with evidence for Early Holocene interaction between these neighbours, gives cause for us to question some authors continued adherence to a singular narrative of the Austronesian Hypothesis and the ‘Neolithisation’ of this part of the world. It also leads us to suggest that the forests of this vast region are, to an extent, a cultural artefact.In Europe, Southwest Asia and adjoining regions, the Early Neolithic is the time when hunting and gathering economies were replaced (through a variety of mechanisms) by economies based on farming, with a small initial ‘package’ of cereal crops (wheat, barley, oats) joined through most of its dispersal by domesticated animals (cattle, sheep/goats, pigs) (Barker, 1985 and Bellwood, 2005). This change was accompanied by profound reorganisations of society and material culture and thus is regarded as one of the great discontinuities in human prehistory. It was visible as a significant event to researchers very early in the development of archaeology – Gordon Childe, 1925 and Childe, 1934 dubbed it the ‘Neolithic Revolution’. The spread of Neolithic farming in Europe appears to have been accompanied by a certain level of relocation of genetic groups (e.g. Cavilli-Sforza et al., 1988, Richards, 2003 and Soares et al., 2010). Suggested changes in population density may perhaps have been mediated by the differences in carrying capacity between foraging and farming systems. These were interpreted by some as a ‘push-factor’ that would fuel the spread of population and economic systems (Bellwood and Renfrew, 2002; although see recent discussions of these models, e.g. Zeder, 2012). The ability to generate a storable food surplus enabled the development of more complex societies and craft specialisations impossible in hunting and gathering economies in these regions.
A similar pattern of Neolithic spread, with movement of crops and genetic material, has been asserted for other parts of the world (Bellwood and Renfrew, 2002 and Bellwood, 2005). One powerful example of the application of European-influenced Neolithic models has been the ‘Austronesian Hypothesis’ (e.g. Bellwood, 1985 and Bellwood, 1988, Bellwood, 1997, Bellwood, 2005, Bellwood, 2011, Diamond, 2001, Diamond and Bellwood, 2003 and Spriggs, 2011) where apparently convergent linguistic and archaeological evidence was interpreted to indicate a diaspora of Austronesian-speaking, rice-growing agricultural people from Taiwan some 5000 years ago. These people are argued to have spread across many of the islands of the Sunda Shelf – the great archipelago of Island Southeast Asia (Fig. 1), acquiring tree crops and losing rice on the way, before dispersing further to Madagascar and across the Pacific Islands. The hypothesis has been very persuasively argued, has considerable explanatory power and has been extremely influential. There is no doubt that there is a cogent and factual basis to the argument: many peoples across a vast region of the Earth's surface share cognate languages and genetic material, and the archaeological footprint of the early inhabitants of most of the Pacific islands, with characteristic artefacts, including pottery, is also incontrovertible.
It has been argued, however, (Terrell et al., 2001, Donohue and Denham, 2010, Blench, 2010 and Barker and Richards, 2012) that the coherence and strong explanatory power of this narrative have led to the eclipse of earlier views of the prehistory of the region including the ‘Nusantao Hypothesis’ of Solheim (1984) and have subsequently channelled and constrained debate about other interpretations of the evidence. Solheim (1984) had argued that people living on the emergent Sunda Shelf in the Early Holocene were forced by sea-level rise to become maritime, and that marine interaction would have led to linguistic and cultural similarities such as the ‘Kalnay’ ceramic tradition and the exchange of agricultural resources.
Amongst others, Terrell et al., 2001 and Donohue and Denham, 2010 and Denham (2013) argue that the experience of the archaeological community in Europe and Southwest Asia had shaped expectations and discourses in mainland and island Southeast Asia, where events had been seen through the lens of a Eurocentric group of concepts and assumptions. They argue – as have others since Gorman, 1970 and Gorman, 1971 – that the lens of ideas generated from events in European prehistory should not be used uncritically to examine developments in other areas.
In the last ten years, emerging genetic, linguistic and archaeological/palaeobotanical evidence (for instance Paz, 2002, Barton and Paz, 2007, Soares et al., 2008, Soares et al., 2011, Bulbeck, 2008, Blench, 2010, Denham et al., 2009a and Denham et al., 2009b; Donohue and Denham, Donohue and Denham, 2010 and Donohue and Denham, 2011; Barker et al., 2011, Barker and Richards, 2012 and Denham, 2013) suggests that alternative interpretations may have currency in the wider region. Here we review indications of change in landscape management and food production strategies during the Holocene across the vast area of Island and mainland Southeast Asia (hereafter, ‘the region’ or ‘the lands around the Sunda rim’). At first Western contact, a huge range of strategies existed and many persist in modern times. Many of these are intimately bound up with sophisticated systems of forest management (Wiersum, 1997) and resource use and it is becoming possible to suggest they have an extensive and important prehistoric ancestry in the region (Rabett, 2012).
2. The beginnings of forest management in the region
It is argued here that there is a relatively long prehistory to land management practices in the region, as is now also becoming apparent in neighbouring Sahul (the biogeographic region encompassing the easternmost Indonesian islands, New Guinea and Australia). Pollen, charcoal and archaeology suggest that repeated biomass burning to produce productive forest-edge environments seems to have appeared ∼50,000 years ago, shortly after the arrival of the first modern human populations (Hope, 1998, Hope, 2009, Haberle, 1998, van der Kaars et al., 2000, Hunt et al., 2007, Hunt et al., 2012 and Summerhayes et al., 2010; Lentfer et al., 2010), although Kershaw et al. (1997) and van der Kaars et al. (2001) suggest an approximate date of ∼65,000 years for the beginning of biomass burning in Java. Regular fire in Late Pleistocene savannahs is suggested in NE Thailand by Penny (2001) and during the latest Pleistocene in grassy vegetation at low altitude in West Java by van der Kaars et al. (2001). In both cases, though, it is unclear whether this reflects human activity.
3. Traditional forest management and cultivation in the region
It was an assumption – almost an article of faith – amongst many biogeographers, ecologists and palaeoecologists that the great regional rainforests were, at Western contact, the product of natural climatic, biogeographic and ecological processes (e.g. Flenley, 1979 and Morley, 2000). It was widely thought that peoples living in the rainforest caused little change to vegetation outside localised areas of ‘slash and burn’. This is implicit also in anthropological debates about the viability of pure forager lifestyles in lowland tropical forests (e.g. Headland, 1987, Hutterer, 1988, Bailey et al., 1989, Townsend, 1990, Bailey and Headland, 1991 and Dentan, 1991).
This stereotype seems to be far from the case: the truly vast extent of ‘well-worked’ secondary forest in Borneo was first noted by Gibbs (1914) and more recent development and anthropological work documents the widespread and highly variable nature of systems of forest management (e.g. Kedit, 1982, Wiersum, 1997, Sellato, 2001, Latinis, 2000 and Janowski, 2004). Although it is evident that these practices were very widespread at first Western contact in the region, their antiquity is uncertain.
A number of points are germane to any understanding of the human use of plants and animals in the region. These include an extremely diverse range of activities, the nature of the economically useful plants (many of which are perennial) and thus the timescales involved in propagation and cultivation systems, the general lack of plant cultivars clearly separated genetically from wild ancestors and the lack of locally-domesticated animals.
3.1. Typology of activity
In the traditional European perspective originating with Childe, 1925 and Childe, 1934, we have a clear typology of ‘foragers’ and ‘farmers’. Although it is readily acknowledged that even today many farmers worldwide might hunt a little and gather the odd wild plant food, the opportunities for this were limited outside the initial period of the expansion of agriculture (however protracted this was – see for instance Gregg, 1988 for an instance of this initial period taking ∼2000 years in Germany). This is simply because the loss of habitat to farming made rare very many wild food organisms. It is otherwise in many of the lands around the Sunda rim, where outside intensive rice-growing areas and modern industrial plantations a very complex situation still obtains. There is, for a start, an extremely wide range of traditional practices of management, manipulation and exploitation of forest resources. These grade into true arboriculture and include clan forests, catchment protection forests, temple forests and sacred groves, taboo and protected trees, species-enriched forests, enriched fallows, forest gardens, smallholder plantations and home gardens (Kedit, 1982, Brosius, 1991, Wiersum, 1997 and Latinis, 2000; Salafsky, 1994; Mulyoutami et al., 2009; see also Kennedy, 2012 for similar instances in Sahul). Until very recently in Borneo, most farmers obtained meat by hunting because there were no domesticated animals – this is still the case today with traditional groups such as the Kelabit (Janowski, 2004). Further, even groups such as the Kelabit, who recognise themselves as farmers, still gather many wild or semi-wild plant foods and manage the forest. They recognise and maintain as ‘Womens' Forest’ areas of secondary forest, regenerating abandoned fields and places where fruit trees were planted on the sites of abandoned long-houses. In these places women gather fruit, together with edible ferns, leafy plants and fungi. Rotan palms (Calamus spp.) for basketry are also gathered from places in the secondary forest ( Janowski, 2004). Men hunt in areas of old-growth woodland distinct from the ‘Womens' Forest’. On the other hand, the Penan, a group that see themselves and are perceived as purely foragers, actually also participate in forest management by planting seeds of the sago palm in favourable locations ( Kedit, 1982 and Brosius, 1991) and in some circumstances controlling other vegetation in order that the sago palms thrive. Finally, the tropical environment leads to problems for cultivators. Monocultures typically become rapidly-overcome by weeds unless rigorously weeded and bare soil washes away rapidly ( Kenzo et al., 2010, Anda and Kurnia, 2010 and Valentin et al., 2008), so a characteristic traditional way of growing many food plants is in polyculture, often among trees ( Salafsky, 1994; Mulyoutami et al., 2009). Thus, it is fair to say that the distinctions between ‘wild’ and ‘cultivated’ plants, or between ‘foraging’ and ‘farming’ lifestyles would be at best blurred and at worst meaningless to many people in the lands around the Sunda rim.
3.2. Domestication
As noted above, in the lands around the Sunda Shelf, the distinction between ‘cultivated’ and ‘wild’ was (and often still is) blurred. People such as the Penan will at times select and propagate wild plants in the forest (Kedit, 1982 and Brosius, 1991) and other groups will incorporate wild plants into their plots. There is difficulty in preventing genetic mixing between these selected forms and immediately-adjacent wild populations. The characteristic modifications to food plants for taste and manageability which we call ‘domestication’ did not occur widely, with the notable exception of the hybridisation which led to the modern banana (Carreel et al., 2002; Perrier et al., 2011) and the appearance of sterile clones of the yam (Lebot et al., 2004 and Malapa et al., 2005). Moreover, the sheer variety of plants in the diet (Christensen, 2002) means that few are of overwhelming importance and thus less likely selectively bred. The Barawan, for instance, claim to gather fruit from a different species from the genus Sapindus for every month of the year (COH, pers. obs., 2004) and this genus us only a tiny proportion of their diet. Further, domestication of the native fauna hardly occurred so wild meat remained an important resource.
3.3. The nature of the edible plants
The vast majority of indigenous food plants in the region are herbaceous (either leafy or tuberous) or are trees (Dewar, 2003, Barton and Paz, 2007 and Barton and Denham, 2011). Although several species of wild rice are indigenous and some were most probably exploited (e.g. Kealhofer, 2002 and Barker et al., 2011), domesticated rice was introduced, probably ∼4000 BP when it appears in pottery at Gua Sireh (Bellwood et al., 1992) then a little later at Niah (Doherty et al., 2000). This has a number of implications. For the tuberous and herbaceous crops, harvest is rarely concentrated into a single season. Many fruits do have distinct seasons, but (as noted above for Sapindus spp.), there are fruit species ripening throughout the year. Further, storage (other than short term storage of root crops in the ground) and long-distance transport of many plant foods was not possible and thus precluded the accumulation of surpluses.
3.4. Timescales of activity
Timescales of activity are controlled by the phenology of the food plants. Tree crops typically take many years to mature and become productive (Mulyoutami et al., 2009). One of the authors (COH) recalls meeting a Punan man gathering fruit beneath some huge trees on the heavily-forested riverbank of the Sungai Niah in the Niah National Park, Sarawak, in 2001. He told us “These are my grandfather's trees: he planted them for me and just now they start to give fruit”. Many indigenous root crops also need a cropping cycle more than a year-long (Dewar, 2003).
All of these factors combine to produce patterns of human activity and plant occurrence extremely different from those present in agricultural systems in much of the world. There is a continuum, in practice, between ‘wild’ ecosystems relatively unaffected by human intervention, through various types of augmented and secondary forest, forest gardens, cultivation plots and fields (Wiersum, 1997) and parts of this spectrum may have a considerable prehistory (below). For parts of this spectrum, there are close comparisons with the better-known Holocene systems of New Guinea (for instance Denham et al., 2003, Denham et al., 2009a, Denham et al., 2009b, Denham, 2004, Denham, 2009, Denham, 2011, Denham, 2013, Denham and Haberle, 2008, Kennedy, 2012 and Haberle et al., 2012) where often-related plants and techniques were used.
4. Rainforest use and the palynological signal
It is extremely difficult to recognise the archaeological signature of past human activity in tropical environments because much it seems to have involved perishable materials with few or no stone and ceramic artefacts. Highly-visible stone structures appeared only in the last few millennia. Further, dense vegetation and litter layers make ground survey difficult and thick tree canopies limit aerial exploration (Hunt et al., 2012).
A common approach to recognise human activity elsewhere is to decode palaeoenvironmental records for anomalies indicative of human activity. Many palynologists working in the region have suggested that human activity is visible in their records (see for instance. Maloney, 1980, Maloney, 1999, Newsome and Flenley, 1988, Kealhofer and Penny, 1998, Flenley and Butler, 2001, Maxwell, 2001, Maxwell, 2004, White et al., 2004, Hunt and Rushworth, 2005 and Hunt and Premathilake, 2012), usually because palynological records contain episodes characterised by pollen of disturbance indicators and abundant microscopic charcoal. The approach of examining records for disturbance indicators and charcoal is analogous to the approach used by palynologists to identify the Neolithic in temperate latitudes (see, for instance authors cited in Whitehouse et al., 2014). This information has rarely been examined systematically on a regional scale, however, except for the synthesis for Thailand by Kealhofer (2002) and wider discussion by Maloney (e.g. Maloney, 1998).
This approach is likely to produce a signal in relatively stable conditions in the middle and later Holocene. There is, however, considerable difficulty in differentiating anthropogenic clearance activity from natural fire caused by lightning strike unless pollen of cultivars or some other form of distinctive evidence such as phytoliths is present, or if archaeological evidence contemporary with the disturbance is present nearby. Unfortunately, few cultivated taxa in the region produce distinctive pollen. In this case, only pollen of taxa outside their geographical area of origin can be accepted as propagated by humans.
In the earlier literature, microscopic ‘charcoal’ was often taken as evidence for fire and this in turn is often interpreted as a marker for human disturbance of ecosystems. This is, of course, problematic (see for a critique Penny and Kealhofer, 2005 and recent discussions of charcoal analysis e.g. by Whitlock and Larsen, 2007). Selective vegetation modification by fire does not necessarily require big extensive fires – observation of a shifting cultivator in Niah National Park in 2002 by COH showed him using very small fires to burn through individual buttress roots of a mature forest tree until it fell. The procedure produced remarkably little smoke and charred wood. By no means all microcharcoal has an anthropogenic origin, as fire plays a natural part in many tropical ecosystems, particularly during droughts (Goldammer and Seibert, 1989), and is often associated with El Niño (Maxwell, 2004). Further, ‘microcharcoal’ is not just generated by fire. Thermally mature (charred) matter of all types is highly durable even in tropical environments and material of geological origin may be liberated from sedimentary bedrock or old soils by erosion (Hunt et al., 2012).
The nature of the wild edible economically-useful and cultivated plants discussed above also has implications for the palynologist and palaeobotanist. Because the cultivated plants were still mostly morphologically indistinguishable from wild relations, using the occurrence of characteristic cultivated plant morphologies, as is done in many parts of the world, to distinguish economic activity and particularly cultivation per se is next to impossible. The position is exacerbated because in many traditional cultivation systems wild foods are still important. Furthermore, some plants are palynologically invisible: for instance many yams do not often produce pollen and bananas produce pollen which does not preserve.
5. Using interrupted successions to identify human activity in the Early Holocene
Patterns of anthropogenic activity in tropical forest ecosystems may also be recognised by contrasting the palaeoenvironmental record with well-understood models of vegetation change and particularly with the signal from natural successions, unaffected by human intervention. It is a contention of this paper that natural Early Holocene successions are rather rare in the lands around the Sunda rim, except in places which people are most likely to have avoided, such as the hydroseral successions of the great raised mires. The raised mires (e.g. Anderson, 1963; Anderson and Muller, 1975, Page et al., 1999 and Page et al., 2004) characterise much lowland terrain and are characterised by very low nutrient status, with both animal and plant food resources for humans very sparsely available. A good example of the type of Holocene succession that might be expected without human intervention in the region is given by de Boer et al. (2013) for montane forest in the very-isolated island of Mauritius, which has no Early Holocene archaeology. There, Late Pleistocene assemblages are characterised by Nuxia, Weinmannia, Tambourissa purpurea, Erica, and Cycadaceae, with Syzygium, Pilea/Ficus type, Artemisia, and Pandanus. At 11,500 cal. BP, Artemisia disappeared and Erica became rare. Syzygium, Psiloxylon mauritianum and Cycadaceae became briefly important, with some Cyathea, T. purpurea, Allophyllus and Olea present. At 9600 cal. BP, Cycadaceae and Syzygium became rare and are succeeded by Eugenia, Dracaena type and Securinega type, with Arecaceae, Pandanus, Psiloxylon, Nuxia and Weinmannia and some Aphloia, T. purpurea, Allophyllus, Molinaea and Sapindaceae. At 8500 cal. BP, Eugenia, Nuxia and Weimannia became rare, Pandanus declines and Sapotaceae expand ( de Boer et al., 2013). In this tropical forest, taxa follow one another in dominating the environment as a response to changing temperature and rainfall and to the dynamics of interspecies competition. This type of changing species dominance – a climatically-driven succession ( Fig. 2A) – is familiar to palaeoecologists studying the Early Holocene over much of the planet. Typical early Holocene pollen diagrams. A., Kanaka Crater, Mauritius, showing a clear early Holocene succession, with a sequence of taxa dominating the vegetation (after de Boer et al., 2013). B., Rawang Sikijang, Sumatra, with a disrupted succession with the disturbance indicators Celtis, Macaranga, Trema and Poaceae common from the base of the Holocene and expanding ∼8 ka BP (after Flenley and Butler, 2001). As such, one way to test for the presence of human intervention in the forests around the Sunda rim would be to log the extent of disrupted successions and of climatically-driven successions during this period. If a climatically-driven succession is present, this would imply that natural processes were not constrained by human activity. The alternative would be that humans were disrupting natural succession through burning and other activities, as has been suggested at Loagan Bunut in Borneo. At that site, located ∼40 km inland from the shores of the South China Sea, the 40 m core commences at ∼11,200 cal. BP and contains no recognisable climatically-driven succession (Hunt and Premathilake, 2012). Disturbance indicators and abundant charred organic matter are present from the base of the profile. Pollen from sago palms is present from the outset and the eastern Indonesian/New Guinea sago palm Metroxylon appears from ∼10,400 cal. BP, leading one to suppose the import of this species and that sago was being propagated. This may have been no more than the ‘plant and leave’ practised today by some Penan groups ( Kedit, 1982), or possibly it was more akin to a form of active management, such as that recorded by Kennedy (2012). Other sago species occurring later in the Early Holocene at Loagan Bunut include Caryota (which according to Penan informants interviewed by Kedit (1982: 257) provides the most desirable sago) and the sugar palm Arenga. Given that some form of arboriculture using Metroxylon was occurring, it is at least conceivable that the system also incorporated the other sago species, particularly as Eugeissona was outside its normal lower montane forest range in Borneo, thus seeming to imply human intervention. There are other economically-useful taxa in the Loagan Bunut record, including Areca, Mangifera, Cucurbitaceae and Murraya cf. paniculata, but whether they were propagated, or indeed utilised, cannot be demonstrated from present evidence. Also present throughout the sequence are very abundant rice phytoliths, many of which are burnt ( Barker et al., 2011). Given the taxonomic uncertainty surrounding rice phytoliths, it is by no means clear which of the species of rice was present (the morphological variation would suggest that possibly two species were present), but the fact that they are consistently very abundant and that many are burnt might suggest that part of the land management strategy of the people at Loagan Bunut may have involved some maintenance of open areas on the low-salinity fringes of the estuary by regular burning, presumably to exploit stands of wild rice. This type of activity chimes with the patterns seen in the Early Holocene in the Yangtze Delta in China, where fire was used to maintain stands of rice ( Zong et al., 2007, Innes et al., 2010 and Shu et al., 2010). Burning, forest disturbance, pollen of sago palms and rice phytoliths persist at Loagan Bunut until sedimentation ended a little after ∼7000 cal. BP ( Hunt and Premathilake, 2012), suggesting that this was a long-lived and stable system of land management, which must have been at least partly for food production. These data support our proposition that disruption of Early Holocene successions can serve as a favourable proxy for human intervention in rainforest habitats of this region. A full survey of pollen diagrams of Early Holocene age is given in Table 1. This shows that in some areas, for instance Sumatra, lowland West Java, Borneo and Vietnam, there is clear evidence that natural successions were repeatedly disrupted. The disrupted successions are usually accompanied by high incidences of disturbance indicators (typically Poaceae, Macaranga, Mallotus, Trema, Celtis, Compositae – see for example the ecological work of Slik et al., 2003 and Slik et al., 2008). These are present close to the base of the Holocene at some localities, but at other places they appear later. This is very apparent in Sumatra ( Table 1; Fig. 2B), where disruption starts at ∼10,500 at Tao Sipinggan ( Maloney, 1996), then at ∼9600 cal. BP at Danau Padang ( Morley, 1982), around ∼8000 cal. BP at Rawang Sikijang ( Flenley and Butler, 2001) and Pea Sim-Sim ( Maloney, 1980), but not until ∼7500 cal. BP at Pea Bullok ( Maloney and McCormack, 1996 and Maloney, 1996). This general pattern might be expected as human activity spread out over time but does not chime well with an alternative hypothesis of climate-driven fire disruption of forest. At some locations, however, disruption does not occur, and/or disturbance indicators appear very late (e.g. Maxwell, 2001 and Maxwell, 2004).
Nema komentara:
Objavi komentar