Tackling the mangrove restoration challenge.

Mangroves have been converted and degraded for decades. Rates of loss have declined over the past decades, but achieving resilient coastlines requires both conservation and restoration. Here, we outline the challenges for the global restoration of mangroves and what actions could enhance restoration. Ambitious global targets for mangrove restoration, if successful, could deliver global benefits of carbon sequestration, fisheries production, biodiversity, and coastal protection. However, large-scale mangrove planting efforts have often failed, and smaller projects may not deliver landscape-scale benefits, even though they are more suited to community management. Solutions to achieving global targets include reducing risks of large projects and increasing the uptake and effectiveness of smaller projects. Sustainable mangrove restoration requires investment in capacity building in communities and institutions, and mechanisms to match restoration opportunities with prospective supporters and investors. Global reporting standards will support adaptive management and help fully understand and monitor the benefits of mangrove restoration.

The Policy Implications of the Dasgupta Review: Land Use Change and Biodiversity: Invited Paper for the Special Issue on "The Economics of Biodiversity: Building on the Dasgupta Review" in Environmental and Resource Economics.

The "Dasgupta Review" of the economics of biodiversity (Dasgupta 2021) identifies many factors that threaten the ecological sustainability of our economies. This article examines how two policy failures - the underpricing and underfunding of nature - influence global land use change and terrestrial biodiversity loss. If natural areas are priced too cheaply, then converting them to agriculture, forestry and other land uses is less costly than protecting or preserving habitats. Underfunding nature further reduces the incentives for conservation and restoration. The current global funding gap for biodiversity is just under $900 billion annually, and especially impacts developing countries. Ending the underpricing of natural landscape requires removing environmentally harmful subsidies and adopting policies that place an additional cost on the use of land and natural resources or on pollution. Overcoming the funding gap means expanding public and private sources of financing nature, particularly for poorer countries, such as biodiversity offsets, payments for ecosystem services, debt-for-nature swaps, green bonds, sustainable supply chains and international environmental agreements. Using the example of peatlands, the article shows how such a comprehensive global strategy can be built.

Mangroves and coastal topography create economic "safe havens" from tropical storms.

Evidence suggests that mangroves protect economic activity in coastal areas. We estimate this protection from mangroves and coastal elevation globally, examining both "direct" and "indirect" exposure events (< 100 km vs. ≥ 100 km distance from a cyclone's "eye", respectively). We find that higher elevation (≥ 50 m) or wide mangroves (≥ 10 m seaward width) alone shelter economic activity from indirect cyclone exposure, whereas protection from direct cyclone exposure occurs only in high elevation communities with wide mangroves. Our results reveal that the majority of these "safe havens" are in upper middle-income countries but provide significant benefits to populations in lower middle-income countries.

Habitat loss and the risk of disease outbreak.

Evidence suggests that emerging infectious diseases, such as COVID-19, originate from wildlife species, and that land-use change is an important pathway for pathogen transmission to humans. We first focus on zoonotic disease spillover and the rate at which primary human cases appear, demonstrating that a potential outbreak is directly related to the area of wildlife habitat. We then develop a model of the costs and benefits of land conversion that includes the effect of habitat size on the risk of disease outbreak. Our model and numerical simulations show that incorporating this risk requires more wildlife habitat conservation in the long run, and how much more should be conserved will depend on the initial habitat size. If the area is too small, then no conversion should take place. Any policy to control habitat loss, such as a tax imposed on the rents from converted land, should also vary with habitat area.

Sustainability and development after COVID-19.

Developing countries are highly vulnerable to the COVID-19 pandemic, in part due to the lack of international support for ensuring progress towards the 17 Sustainable Development Goals (SDGs). Yet the mounting financial burden faced by all countries means that additional support is unlikely to be forthcoming in the near future. It is critical that developing countries find innovative policy mechanisms to achieve sustainability and development aims in a cost-effective manner. This requires identifying affordable policies that can yield immediate progress towards several SDGs together and aligns economic incentives for longer term sustainable development. We identify three policies that meet these criteria: a fossil fuel subsidy swap to fund clean energy investments and dissemination of renewable energy in rural areas; reallocating irrigation subsidies to improve water supply, sanitation and wastewater infrastructure; and a tropical carbon tax, which is a levy on fossil fuels that funds natural climate solutions. Such innovative and cost-effective policy mechanisms do not require substantial external support, and they foster greater progress towards achieving the SDGs in poorer economies.

Greening the Post-pandemic Recovery in the G20.

Rebuilding G20 economies after the COVID-19 pandemic requires rethinking what type of economy we need and want in the future. Simply reviving the existing 'brown' economy will exacerbate irreversible climate change and other environmental risks. For G20 economies, investing in a workable and affordable green transition is essential. A good place to start is learning what worked and what did not from previous efforts to green the economic recovery during the 2008-2009 Great Recession, examining the cases of the United States and South Korea. Policies for a sustained economic recovery amount to much more than just short-term fiscal stimulus. Transitioning from fossil fuels to a sustainable low-carbon economy will require long-term commitments (5-10 years) of public spending and pricing reforms. The priorities for public spending include support for private sector green innovation and infrastructure, development of smart grids, transport systems, charging station networks, and sustainable cities. Pricing carbon and pollution, and removing fossil-fuel subsidies, can accelerate the transition, raise revenues for the necessary public investments, and lower the overall cost of the green transition.

Rebuilding marine life.

Sustainable Development Goal 14 of the United Nations aims to "conserve and sustainably use the oceans, seas and marine resources for sustainable development". Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits that society receives from a healthy ocean. Here we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures-including climate change-are mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, an ethical obligation and a smart economic objective to achieve a sustainable future.

Mangroves shelter coastal economic activity from cyclones.

Mangroves shelter coastlines during hazardous storm events with coastal communities experiencing mangrove deforestation are increasingly vulnerable to economic damages resulting from cyclones. To date, the benefits of mangroves in terms of protecting coastal areas have been estimated only through individual case studies of specific regions or countries. Using spatially referenced data and statistical methods, we track from 2000 to 2012 the impact of cyclones on economic activity in coastal regions inhabited by nearly 2,000 tropical and subtropical communities across 23 major mangrove-holding countries. We use nighttime luminosity to represent temporal trends in coastal economic activity and find that direct cyclone exposure typically results in permanent loss of 5.4-6.7 mo for a community with an average mangrove extent (6.3 m per meter of coastline); whereas, a community with more extensive mangroves (25.6 m per meter of coastline) experiences a loss equivalent to 2.6-5.5 mo. These results suggest that mangrove restoration efforts for protective benefits may be more cost effective, and mangrove deforestation more damaging, than previously thought.

Restoration and repair of Earth's damaged ecosystems.

Given that few ecosystems on the Earth have been unaffected by humans, restoring them holds great promise for stemming the biodiversity crisis and ensuring ecosystem services are provided to humanity. Nonetheless, few studies have documented the recovery of ecosystems globally or the rates at which ecosystems recover. Even fewer have addressed the added benefit of actively restoring ecosystems versus allowing them to recover without human intervention following the cessation of a disturbance. Our meta-analysis of 400 studies worldwide that document recovery from large-scale disturbances, such as oil spills, agriculture and logging, suggests that though ecosystems are progressing towards recovery following disturbances, they rarely recover completely. This result reinforces conservation of intact ecosystems as a key strategy for protecting biodiversity. Recovery rates slowed down with time since the disturbance ended, suggesting that the final stages of recovery are the most challenging to achieve. Active restoration did not result in faster or more complete recovery than simply ending the disturbances ecosystems face. Our results on the added benefit of restoration must be interpreted cautiously, because few studies directly compared different restoration actions in the same location after the same disturbance. The lack of consistent value added of active restoration following disturbance suggests that passive recovery should be considered as a first option; if recovery is slow, then active restoration actions should be better tailored to overcome specific obstacles to recovery and achieve restoration goals. We call for a more strategic investment of limited restoration resources into innovative collaborative efforts between scientists, local communities and practitioners to develop restoration techniques that are ecologically, economically and socially viable.