Clusters of galaxies: setting the stage

Clusters of galaxies are self-gravitating systems of mass ~10^14-10^15 Msun. They consist of dark matter (~80 %), hot diffuse intracluster plasma (< 20 %) and a small fraction of stars, dust, and cold gas, mostly locked in galaxies. In most clusters, scaling relations between their properties testify that the cluster components are in approximate dynamical equilibrium within the cluster gravitational potential well. However, spatially inhomogeneous thermal and non-thermal emission of the intracluster medium (ICM), observed in some clusters in the X-ray and radio bands, and the kinematic and morphological segregation of galaxies are a signature of non-gravitational processes, ongoing cluster merging and interactions. In the current bottom-up scenario for the formation of cosmic structure, clusters are the most massive nodes of the filamentary large-scale structure of the cosmic web and form by anisotropic and episodic accretion of mass. In this model of the universe dominated by cold dark matter, at the present time most baryons are expected to be in a diffuse component rather than in stars and galaxies; moreover, ~50 % of this diffuse component has temperature ~0.01-1 keV and permeates the filamentary distribution of the dark matter. The temperature of this Warm-Hot Intergalactic Medium (WHIM) increases with the local density and its search in the outer regions of clusters and lower density regions has been the quest of much recent observational effort. Over the last thirty years, an impressive coherent picture of the formation and evolution of cosmic structures has emerged from the intense interplay between observations, theory and numerical experiments. Future efforts will continue to test whether this picture keeps being valid, needs corrections or suffers dramatic failures in its predictive power.Comment: 20 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 2; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

Green governmentality and swidden decline on Palawan Island

Environmental governance initiatives increasingly extend to the rural Philippines as ‘devolved’ programmes that progress livelihood change, differentiation and market-based investments. This paper examines how the origins, rise and consequences of environmental governance initiatives in Palawan Island, the Philippines, facilitate forms of governmentality that intersect with, and rearticulate through, the local political economy to influence swidden-based livelihoods, social relations and landscape composition. Drawing on recent scholarship, I describe how the rise and substance of this governance agenda manifests spatially as a form of discursive green governmentality. I argue that this scaled, discursive process involves diverse institutions that decentre and deploy technical knowledge, values and rules in local spaces, influencing how farmers self-govern their behaviour and use of nature toward ‘sustainability’ (Goldman 2001). I draw on a case study to show how Tagbanua swidden farmers negotiate such green governmentality by adopting new landscape ideals through anti-swidden narratives inflected by local politics, economy and environmental change in villages around the Puerto Princesa Subterranean River National Park. I focus on how green governmentality has become systemic across scales to converge with local politics and economy, where governmental discourse is pliable, flexibly interpreted, though followed to affect the shift from long fallow to permanent cultivation. I conclude by showing that the ways government, non-governmental and local actors communicate and invest in such discourse facilitates convergence with the local political economy, reinforcing swidden decline, livelihood risk and marginalisation

How Biodiversity Conservation Policy Accelerates Agrarian Differentiation: The Account of an Upland Village in Vietnam

This paper shows how the implementation of Vietnam«SQ»s recent biodiversity conservation policy in Ba Vi National Park has increased the economic value of nature, created sustained conflict, and exacerbated agrarian differentiation in an upland village in northern Vietnam. Increased global and national interest in biodiversity conservation has intersected with markets for ecosystem services that attempt to commoditise biodiversity resources in Ba Vi National Park and reconfigure conservation as market-based development. Efforts to marketise conservation have simultaneously increased the financial value of forestland and drawn new capital investments. In Ba Vi, local elites have captured these new forms of wealth through their connections to political parties, reinforcing the already unequal distributions of wealth and power. Coupled with political power, rising land value has also allowed local elites to become landlords, with the capacity to further dispossess other villagers. The resulting skewed access to natural resources has widened the gap between poor and wealthy villagers, and contributes to their over-exploitation of forests within the Park through informal agricultural expansion. The ensuing local conflicts have also negatively affected livelihoods and biodiversity resources

The Social Life of Forest Carbon: Property and Politics in the Production of a New Commodity

Interventions to conserve carbon stored in forests are central to the emerging global climate change regime. Widely referred to as REDD+, these interventions engage local resource holders in contracts to restrict their use of land and forests in exchange for conditional benefits, effectively creating a market for forest carbon—a new and intangible commodity. Delving into the social and material implications of this, three case studies (Papua New Guinea, Philippines, Cambodia) examine property relations in the early stages of forest carbon production in different tenure contexts. The case studies reveal that: (a) the risk of local exclusion from forest and lands under REDD+ is real, but is mediated by dynamic negotiations over knowledge and property; (b) the relationship between forest carbon and underlying property relations around land and forests is recursive and mutually constitutive; and (c) due to ongoing and entrenched property contests in REDD+ locations, there remains an unstable foundation for forest carbon market

The impact of swidden decline on livelihoods and ecosystem services in Southeast Asia: A review of the evidence from 1990 to 2015

Global economic change and policy interventions are driving transitions from long-fallow swidden (LFS) systems to alternative land uses in Southeast Asia's uplands. This study presents a systematic review of how these transitions impact upon livelihoods and ecosystem services in the region. Over 17 000 studies published between 1950 and 2015 were narrowed, based on relevance and quality, to 93 studies for further analysis. Our analysis of land-use transitions from swidden to intensified cropping systems showed several outcomes: more households had increased overall income, but these benefits came at significant cost such as reductions of customary practice, socio-economic wellbeing, livelihood options, and staple yields. Examining the effects of transitions on soil properties revealed negative impacts on soil organic carbon, cation-exchange capacity, and aboveground carbon. Taken together, the proximate and underlying drivers of the transitions from LFS to alternative land uses, especially intensified perennial and annual cash cropping, led to significant declines in pre-existing livelihood security and the ecosystem services supporting this security. Our results suggest that policies imposing land-use transitions on upland farmers so as to improve livelihoods and environments have been misguided; in the context of varied land uses, swidden agriculture can support livelihoods and ecosystem services that will help buffer the impacts of climate change in Southeast Asia