Sarah Hülsen


Last Name

Hülsen

First Name

Sarah

ORCID

0000-0002-8899-0074

Organisational unit

09576 - Bresch, David Niklaus / Bresch, David Niklaus

Filters

2022 - 20255
Reset filters

Search Results

Publications 1 - 5 of 5
  • How many people do coastal ecosystems protect from tropical cyclones globally?
    Item type: Master Thesis
    Hülsen, Sarah (2022)
    Natural Climate Solutions (NCS) are key to climate change mitigation, but can also deliver important co-benefits, such as disaster risk reduction and adaptation to climate change. Previous research has used a variety of methods to assess NCS and ecosystem-based risk reduction. The overarching question this thesis aims to answer is: How many people do coastal ecosystems protect from the impacts of tropical cyclones and resulting storm surges? The combination of event-based risk modelling and ecosystem modelling data is a novel approach. This research uses the probabilistic model CLIMADA and ecosystem service data to quantify the coastal protection provided by coastal ecosystems. First, a baseline of the number of people impacted by tropical cyclones in the low-elevation coastal zone and the number of people simultaneously within the protection distance of coastal habitats is established. Next, the baseline is compared with historical habitat and population data from 1992. Looking to the future, we investigate changes in coastal protection under climate change (SSP585 in 2050). Finally, scenarios of different options for human action in protecting, managing, and restoring nature in the near future (2050) are appraised: continued forest conversion, agroforestry, mangrove restoration, and reforestation. The current number of people in the low-elevation coastal zone protected from tropical cyclones by coastal habitats is 13.84 million, which corresponds to approximately a quarter of all people impacted by tropical cyclones in this zone. Historically, the share of people protected has decreased by approximately 4%, both due to population developments, as well as habitat loss. The average numbers of people impacted and protected annually will increase up to 40% with climate change, however, there is a slight decrease in the share of people protected. Protecting, managing, and restoring nature is important to prevent a further decrease in protection, on a global scale, but especially on a local level. While the number of people protected globally only increases slightly across the nature management and protection scenarios, protection in individual countries can increase by up to 31% - 37% under reforestation and mangrove restoration respectively, and up to 6% under agroforestry. The findings of form an important basis for policy and the use of NCS for disaster risk reduction, e.g. by highlighting areas which have both a need for protection and a potential for NCS.
  • Mangroves and their services are at risk from tropical cyclones and sea level rise under climate change
    Item type: Journal Article
    Hülsen, Sarah; Dee, Laura E.; Kropf, Chahan Michael; et al. (2025)
    Communications Earth & Environment
    Climate change is expected to alter the frequency and intensity of extreme events, modifying the natural disturbance regimes to which ecosystems are adapted. Here, we present a spatially explicit risk index for mangroves and associated biodiversity and ecosystem services based on projected frequency changes of tropical cyclone wind speeds and rates of relative sea level rise under SSPs 245, 370 and 585 by 2100. Globally, approximately half of the total mangrove area (40–56% depending on the SSP) will be at high to severe levels of risk due to climate-modified tropical cyclone disturbance regimes. Further, we find mangrove areas with high levels of biodiversity and ecosystem services provision, including coastal protection for people and assets, carbon sequestration, and fishery benefits, are at proportionally higher levels of risk. Our findings emphasize the need to anticipate changes in natural disturbance regimes and adapt ecosystem management to sustain mangroves and their services in the future.
  • Global protection from tropical cyclones by coastal ecosystems—past, present, and under climate change
    Item type: Journal Article
    Hülsen, Sarah; McDonald, Robert I.; Chaplin-Kramer, Rebecca; et al. (2023)
    Environmental Research Letters
    Coastal ecosystems have the potential to contribute to disaster risk reduction and adaptation to climate change. While previous studies have estimated the value of current coastal ecosystems for reducing coastal risk, there have been relatively few studies that look at changes in ecosystem service provision, in the past and under climate change. We employ the probabilistic, event-based CLImate ADAptation platform (CLIMADA) to quantify the protection from tropical cyclones (TCs) provided by coastal ecosystems, modeling the number of beneficiaries in the past and under future climate change. We also investigate the potential of nature-based solutions (NbS), such as mangrove restoration. We find that currently, one in five (21%) of all people impacted annually by TCs in the global low-elevation coastal zone is within the protection distance of coastal ecosystems. Over the last 30 years, the share of protected people has decreased by approximately 2%, due to ecosystem loss. With climate change, the average annual number of people impacted will increase by 40%. Simultaneously, the proportion of people protected by coastal ecosystems with climate change decreases due to changes in TC distribution (−1%). The importance of current coastal protection, and the potential for increasing protection by NbS, varies widely between countries. While the number of people protected globally only increases slightly with mangrove restoration, the share of people protected in individual countries can increase by up to 39%. Our findings provide a basis for NbS planning and adaptation policy, by highlighting areas which will be crucial for coastal protection services in a world altered by climate change.
  • Win-wins or trade-offs? Site and strategy determine carbon and local ecosystem service benefits for protection, restoration, and agroforestry
    Item type: Journal Article
    McDonald, Robert I.; Chaplin-Kramer, Rebecca; Mulligan, Mark; et al. (2024)
    Frontiers in Environmental Science
    Nature-based solutions (NBS) can deliver many benefits to human wellbeing, including some crucial to climate adaptation. We quantitatively assess the global potential of NBS strategies of protection, restoration, and agroforestry by modeling global climate change mitigation and local ecosystem services (water availability, sediment retention, runoff, pollination, nitrogen retention, green water storage, and coastal protection). The strategies with the most potential to help people do not necessarily deliver the most climate change mitigation: per area of conservation action, agroforestry provides substantial benefits (>20% increase in at least one local ecosystem service) to three times more people on average than reforestation while providing less than one tenth the carbon sequestration per unit area. Each strategy delivers a different suite of ecosystem service benefits; for instance, avoided forest conversion provides a strong increase in nitrogen retention (100% increase to 72 million people if fully implemented globally) while agroforestry increases pollination services (100% increase to 3.0 billion people if fully implemented globally). One common disservice shared by all the NBS strategies modeled here is that increased woody biomass increases transpiration, reducing annual runoff and in some watersheds negatively impacting local water availability. In addition, the places with the greatest potential for climate change mitigation are not necessarily the ones with the most people. For instance, reforestation in Latin America has the greatest climate change mitigation potential, but the greatest ecosystem service benefits are in Africa. Focusing on nations with high climate mitigation potential as well as high local ecosystem service potential, such as Nigeria in the case of reforestation, India for agroforestry, and the Republic of Congo for avoided forest conversion, can help identify win-win sites for implementation. We find that concentrating implementation of these three conservation strategies in critical places, covering 5.8 million km(2), could benefit 2.0 billion people with increased local ecosystem services provision. These critical places cover only 35% of the possible area of implementation but would provide 80% of the benefits that are possible globally for the selected set of ecosystem services under the NBS scenarios examined here. We conclude that targeting these critical places for protection, restoration, and agroforestry interventions will be key to achieving adaptation and human wellbeing goals while also increasing nature-based carbon mitigation.
  • Beyond single company climate risk disclosure: event-based physical risk reporting
    Item type: Journal Article
    Wattin Håkansson, Victor; Meiler, Simona; Hülsen, Sarah; et al. (2025)
    Environmental Research: Climate
    An increasing number of countries and stakeholders now require large companies to disclose physical climate-related risks. However, the lack of standardization has led to the use of varied risk metrics from different data sources, making it difficult to compare physical risks across companies and preventing investors from aggregating risks at the portfolio level. To address this, we develop an approach using standardized, event-based probabilistic natural catastrophe risk assessments to improve global risk data aggregation and enable customized risk metrics. Integrating these methods into climate physical risk reporting would help investors align portfolios with a risk-return efficient frontier that accounts for physical risks, directing capital toward companies better equipped to manage climate impacts and promoting strategic adaptation. We propose a transparent, replicable, open-source methodology using event-loss tables to present per-event impact data. This approach is illustrated with two fictional companies exposed to tropical cyclone risk under current and future climate scenarios, highlighting the potential for company comparison, and portfolio risk assessment and optimization. Finally, we call on the scientific community and regulators to establish standardized hazard sets and financial loss functions to support transparent comparison and risk aggregation.
Publications 1 - 5 of 5