This report focuses on the impact of environmental degradation on the poorest, and the sustainability of the economic development model. The global pattern of development observed over the past 25 years has yielded impressive returns, but has come at a high cost of environmental degradation. However, the report finds that the environmental costs of development are disproportionately borne by the extreme poor, and that the changing quality of local natural capital plays a determining role in the process of poverty reduction. Importantly, regardless of the definition of sustainability used, the historical model of development does not appear to be sustainable in the poorest areas of the world. Therefore, achieving the World Bank's poverty goals in a sustainable manner will require more aggressive policy changes than are commonly appreciated. No single set of policy recommendations can apply for all countries, as de-coupling economic and poverty alleviation growth from environmental damages depends on the country context. Still, one truism does apply to all countries: the Twin Goals of poverty alleviation and shared prosperity simply cannot be achieved in an economy and environment that is un-sustainable. Maintaining the sustainable use of natural capital and healthy ecosystems is a fundamental part of what countries need to achieve the Twin Goals.