Forests provide a multitude of key benefits to the ecosystem in terms of climate regulation, human health, carbon sequestration, fresh water and air, energy reductions, biodiversity, recreation, aesthetics, along with traditional goods such as timber, fuelwood, and bioenergy. These essential services are the world’s natural capital, and become even more valuable in urban settings where barriers of planning, policy, and logistics impose severe constraints. By quantifying the ecological functions of pollination, biodiversity and biological control that urban forests provide, we can better assess the biotic contribution to natural capital.