Climate change has critically changed the relevance of the traditional knowledge of indigenous groups. Natural signals that were used to trigger activities in the past are now less reliable. As the weather becomes hotter in the tropics, migratory birds come at a different period of the year and the rainy season comes earlier or later than usual, which can lead to a disorientation of people in their daily lives. Additionally, the need for more land to cultivate could also arise in the future due to climate change. For instance when droughts or declining soil fertility diminish crop yields, there may be a need to clear more forest areas and move to other places. Pressures on land from commercial agriculture, including biofuels, and carbon sequestration projects could also cause major land cover changes.
Changes in climate have been sensed by the Dayaks because of various indicators. They observed bird species that they had never seen before, they became aware that the level of water in the rivers is higher/lower than usual for the season and that the traditional plants used as medicinal remedies can not be found anymore. Behaviour and migration patterns of birds have traditionally been used to guide hunting and cultivation activities but they no longer provide reliable guidance.
The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report published in early 2007 confirmed that global climate change is already happening. The report found that communities who live in marginal lands and whose livelihoods are highly dependent on natural resources are among the most vulnerable to climate change. Many indigenous and traditional peoples who have been pushed to the least fertile and most fragile lands as a consequence of historical, social, political and economic exclusion are among those who are at greatest risk.