CC BY 4.0Volf, CarloCarloVolfBueno Unzeta, BrunoBrunoBueno UnzetaEdwards, PeterPeterEdwardsHobday, RichardRichardHobdayMäder, StephanStephanMäderMatusiak, Barbara S.Barbara S.MatusiakWulff, KatharinaKatharinaWulffOsterhaus, WernerWernerOsterhausManoli, GabrieleGabrieleManoliDella Giustina, ChristinaChristinaDella GiustinaJoshi, JasminJasminJoshiKämpf, Jerome H.Jerome H.KämpfVega, KevinKevinVegaKueffer, ChristophChristophKueffer2024-06-032024-06-032024Note-ID: 000056BEhttps://publica.fraunhofer.de/handle/publica/469014https://doi.org/10.24406/publica-314210.1016/j.jum.2024.02.00210.24406/publica-3142Daylight is essential for ecosystems and for the physical and mental well-being of people. In densely populated cities, only a small proportion of total daylight is available to support urban greenery and most people have little daily exposure to natural daylight. Despite this, many cities have followed a strategy of densification as a way of preventing urban sprawl and reducing energy consumption. In this article, we review the biological importance of daylight and show that urban densification leads to a reduction in the daylight available for both people and nature. We conclude that daylight in cities should be treated as a limiting resource that needs to be planned and managed carefully, much like water or energy. We suggest elements for a policy framework aimed at optimizing urban daylight, including how to determine daylight needs, how to determine the maximum viable urban density, and policy options for built and unbuilt areas.enArchitectureDaylightEcosystem servicesGreen cityHealthNature-based solutionsSustainabilityjournal article