**1. Introduction: Indigenous Peoples in Tropical Lowland Rainforests in Southeast Asia**

Southeast Asia is home to a large diversity of indigenous peoples in a wide range of environmental conditions. Though they are often grouped together in terms of their socio-political status as relatively weak and marginal communities within the present nation-states, there are many ways to differentiate between them on the basis of modes of livelihoods, or specific cultural, religious, or linguistic characteristics [1,2]. Here, we focus on four of these groups in order to discuss the present-day challenges that they face as a result of climatic changes, in addition to the impacts of other types of environmental changes brought about by human interventions.

In this article, we discuss some of the practices and the related knowledge about the natural environment and its resources of four indigenous groups in insular Southeast Asia, namely the Agta in the Philippines, and the Orang Rimba, Mentawai, and Ngaju Dayak in Indonesia. We focus on the way these peoples have reacted to external interventions in their home territories and discuss to what extent climate change has been a major factor in the need for adjustment of their way of life. All groups share a similar environment, that is tropical lowland rainforest, with or without a coastal zone. However, their traditional modes of exploitation of this environment have differed substantially,

which can partly be ascribed to its specific characteristics at various locations as well as to the cultural characteristics of these ethnic groups.

The majority of the indigenous peoples in Southeast Asia practice some form of shifting agriculture in either lowland, hilly, or even mountainous environments. Within this group, there are big differences in terms of crops cultivated, and specific methods of practicing this form of land use [3]. In some cases, they also combine shifting agriculture with permanent agriculture, for instance for the cultivation of particular fruit trees or cash crops. There are also relatively small groups of hunter-gatherers to be found in the region's lowland rainforests. Their numbers and densities are always low. To a large extent they hunt, fish, and collect a wide range of products for their own subsistence, but all of them are also involved in the harvesting of non-timber forest products (NTFPs) for commercial purposes and exchange with traders. As hunting and gathering alone usually no longer provide a sufficient basis for their living, most of these groups also engage in small-scale agriculture (usually shifting cultivation), as well as casual labor [4].

Practices of shifting cultivation have often been described in negative terms. Colonial and national government officials in many countries considered this form of using forest resources as being wasteful and inefficient [5]. Policies were formulated to turn these forest cultivators into permanent agriculturalists. A recent volume in a series of books on shifting cultivation, edited by Malcolm Cairns [6], about Shifting Cultivation Policies, which provides numerous case studies from a wide range of countries, proofs this point again. However, scientists of various disciplines, inspired by the monumental work of Conklin [7], have looked into these practices in closer detail and they have reached a different conclusion. They consider the shifting cultivation practiced by many forest-based indigenous communities as being a highly efficient and sustainable way of using available resources, which does not harm forest resources in the long run. In contrast, there are clear indications that small-scale shifting cultivation can positively affect forest biodiversity. This is evident, for instance, from the high number of useful plants and animals that are the result of selective cultivation and breeding [8]. On the other hand, there are also examples in which indigenous communities have overexploited particular plants or animals often because of their commercial value for external markets. An interesting case is how the demand for agarwood (also known as eaglewood or *gaharu*) has brought some *Aquilaria* species, that produce this valuable product to the point of extinction in many forested areas in Southeast Asia [9].

In addition, there is now widespread recognition of the extensive indigenous knowledge about forest ecosystems, including its diversity of plants and animals, soil types, and fertility. The attention for and interest in such knowledge systems has increased very much in recent decades. In fact, various branches of ethno-science, like ethno-ecology, ethno-botany, and ethno-zoology have developed. Of particular interest is also the knowledge and use of medicinal plants by indigenous peoples, which has turned out to be of great value for the development of a wide range of medicines [10]. In addition to this extensive ecological knowledge, many indigenous communities hold knowledge or memories about specific natural hazards, like earthquakes, volcano eruptions, or tsunamis, and this knowledge tends to be passed on to next generations through narratives and oral traditions [11].

In contrast, knowledge about various aspects of climatic conditions and climate change among forest dwelling communities in Southeast Asia appears to be less elaborate, apart from the interpretation of particular indicators of relatively short-term future weather conditions [12,13]. Beyond the experience of extended drought or excessive rainfall, there are few references in indigenous knowledge systems about awareness of long-term variability in temperature or rainfall. This relative absence of knowledge of gradual climatic changes may in itself not be surprising as, especially in the wet tropics, such changes are usually only noticeable on the basis of systematic records kept over extended periods of time. In case these changes become more extreme, like the frequency and intensity of tropical storms, floods, or mudslides, local awareness of them will likely increase.

In other climate zones, where the climatic changes are more evident or pronounced, local knowledge on such changes appears to be more elaborate. Moreover, perceptions of such change by local and indigenous communities have turned out to be quite consistent with studies of climate change based on data collected through the use of instruments. Savo et al. [14] provide an interesting meta-analysis of climate changes observed by hundreds of subsistence-oriented communities from around the globe. This study confirms once more the relevance of traditional ecological knowledge in studying ecosystems including the impact that changes of whatever kind have on the environment and their livelihoods.
