Introduction Increasing urban populations have led to the growth of informal settlements, with contaminated environments linked to poor human health through a range of interlinked pathways. Here, we describe the design and methods for the Revitalising Informal Settlements and their Environments (RISE) study, a transdisciplinary randomised trial evaluating impacts of an intervention to upgrade urban informal settlements in two Asia-Pacific countries. Methods and analysis RISE is a cluster randomised controlled trial among 12 settlements in Makassar, Indonesia, and 12 in Suva, Fiji. Six settlements in each country have been randomised to receive the intervention at the outset; the remainder will serve as controls and be offered intervention delivery after trial completion. The intervention involves a water-sensitive approach, delivering site-specific, modular, decentralised infrastructure primarily aimed at improving health by decreasing exposure to environmental faecal contamination. Consenting households within each informal settlement site have been enrolled, with longitudinal assessment to involve health and well-being surveys, and human and environmental sampling. Primary outcomes will be evaluated in children under 5 years of age and include prevalence and diversity of gastrointestinal pathogens, abundance and diversity of antimicrobial resistance (AMR) genes in gastrointestinal microorganisms and markers of gastrointestinal inflammation. Diverse secondary outcomes include changes in microbial contamination; abundance and diversity of pathogens and AMR genes in environmental samples; impacts on ecological biodiversity and microclimates; mosquito vector abundance; anthropometric assessments, nutrition markers and systemic inflammation in children; caregiver-reported and self-reported health symptoms and healthcare utilisation; and measures of individual and community psychological, emotional and economic well-being. The study aims to provide proof-of-concept evidence to inform policies on upgrading of informal settlements to improve environments and human health and well-being. Ethics Study protocols have been approved by ethics boards at Monash University, Fiji National University and Hasanuddin University. Trial registration number ACTRN12618000633280; Pre-results.

In the developing economies of the Global South, a fundamental challenge in the transition of settlements from rural or periurban to urban is increased environmental contamination as a result of poor sanitation and sanitation management. With governments’ limited ability to connect all neighbourhoods to a city’s existing municipal water, sewerage and other services, decentralised approaches using green infrastructure offer potential to address this challenge. In addition, green infrastructure might facilitate a move towards a holistic response to manage the full water cycle. This paper presents a narrative review of green infrastructure projects, involving constructed wetlands or their variants for wastewater treatment, within vulnerable communities in the Global South. It describes the scale and scope of each project, identifies the challenges of implementation, and reflects on their outcomes for different stakeholder groups. The review demonstrates that decentralised sanitation programs using constructed wetlands for wastewater treatment can provide a range of advantages/benefits/services, dependant on the specific sociocultural, political and biogeophysical contexts of each. Issues of governance and sociocultural appropriateness, rather than technical issues, challenged the implementation of green infrastructure for sanitation in these projects. Projects must be a collaboration between the government, nongovernment organisations and the community. Whether the project is organised from top-down or bottom-up, community consultation is essential. Context will determine the role of the community in the consultation process and the type of information required to guide the design, implementation and governance of the system. In every project to provide decentralised sanitation systems, the community must be participants, not simply beneficiaries.

Informal settlements represent a challenging operational context for local government service providers due to precarious contextual conditions. Location choice and land procurement for public infrastructure raise the complicated question: who has the right to occupy, control, and use a piece of land in informal settlements? There is currently a dearth of intelligence on how to identify well-located land for public infrastructure, spatially and with careful consideration for safeguarding the claimed rights and preventing conflicts. Drawing on a case study of green infrastructure retrofit in seven informal settlements in Makassar, Indonesia, we classify the informal settlers’ land rights into four types: ownership, use, control, and management. This exploratory study uses a typological approach to investigate the spatial dimension of land rights in informal settlements. We introduce non-registrable land interests and the partial, dynamic, and informal land use rights that impact the land procurement for infrastructure retrofit. We also create a simple spatial matrix describing the control/power, responsibilities and land interests of different stakeholders involved in the location decision making for public infrastructure. We argue that without sufficient understanding of non-formal land rights, land procurement proposals for the public infrastructure upgrades can be frustrated by the individual or group claims on the land, making the service provision impossible in informal settlements.

Tension and conflict are endemic to any upgrading initiative (including basic infrastructure provision) requiring private land contributions, whether in the form of voluntary donations or compensated land acquisitions. In informal urban contexts, practitioners must first identify well-suited land for public infrastructure, both spatially and with careful consideration for safeguarding claimed rights and preventing conflicts. At the same time, they need to defuse existing tensions over land ownership and land use rights while negotiating for the potential use of a unit of land for infrastructure. Even in the case of employing participatory methods, land negotiations are never tension-free. Despite the extensive literature on linkages between urban poverty, inefficient land management systems, and land disputes, in both rural and urban settings, land negotiations for community-scale infrastructure retrofit projects (e.g., neighbourhood roads, water and sanitation infrastructure) are yet to be fully explored. Drawing on a case study of a live green infrastructure retrofit project in six informal settlements in Makassar, Indonesia, we establish links to exchange theory, collective action, and negotiation theory to build a reliable analytical framework for understanding and explaining the land negotiations in small-scale infrastructure retrofit practices. We aim to describe and assess the fundamental conditions for land negotiations in an informal urban context and conclude the paper by summarising several key strategies developed and used in the case study area to forge land agreements.