Rethinking Urban Nature : Maintaining Capacity for Ecosystem Service Generation in a Human Dominated World

Sammanfattning: Human action has transformed the major part of the Earth’s ecosystems. A growing human population puts further pressure on dynamic landscapes and resources. Crucially, for the first time in history, most people live in cities and environmental change has become truly global. Developed as part of the sub-global assessments of The Millennium Ecosystem Assessment, this thesis examines anthropogenic effects on our life-support systems, and their altered capacity to generate goods and services of socio-economic value. It incorporates humans into the analysis of ecosystem dynamics and explores new ways to restore, create, and enhance ecosystem services in urban and other fragmented landscapes.The concept of mobile link organisms, i.e. key species that connect habitats and uphold their capacity to generate ecosystem services, is elaborated in relation to ecosystem dynamics and functioning. They are classified into resource, genetic and process linkers (Paper I). One such species, the Eurasian Jay (Garralus glandarius) and its role in oak tree regeneration across habitats, is empirically studied in a park of Stockholm (Paper II). The Jay is found to be pivotal in safeguarding the desired oak dominated landscape but its seed dispersal function requires active management, including of surrounding non-protected habitats. Potentially, a process oriented management approach could reduce costs and vulnerability to disturbances as well as preserve gene flow and diversity on a landscape level. Critical functions for ecosystem resilience performed by mobile links are likely to grow in importance as human impacts increase.The next focus is on ecosystems that are seldom considered in biological conservation and urban green space management. Ecosystem functions and services are identified in three types of culturally maintained land areas: golf courses, residential gardens, and allotments (Paper III). By GIS-assessment, it is established that they amount to 18% of the studied land area in metropolitan Stockholm, i.e. over twice the size of land set aside as protected areas. When these lands are taken into account, the cityscape appears to be greener than indicated by prevailing conservation maps. Focusing on the rapid expansion of golf courses in urban regions, the first major assessment of amphibian and macroinvertebrate fauna confined to golf courses is presented in Paper IV. Threatened species and those more sensitive to eutrophication, tended to be associated with golf ponds relative to ponds of other lands, including nature-protected areas. As to fauna, there was no significant difference between ponds of these different lands.Paper V further investigates culturally maintained areas such as sacred groves and military zones and considers them as under-explored assets for ecosystem and landscape management. They can perform essential complementary ecological functions and may even be instrumental in securing ecosystem services in fragmented landscapes. The social dimension of their sustenance is emphasized and it is argued that such lands and their steward groups should be explicitly incorporated into management through adaptive co-management schemes. Finally, the benefits of planting and managing an introduced alien cacti species (Opuntia spp.) in a highly fragmented landscape are examined by a case study from Madagascar (Paper VI). The cacti provide a range of ecosystem services vital to human subsistence in a location of scarce food and water supplies. Its extensive network of hedges reinforces landscape connectivity, e.g. exchanges between disconnected patches of sacred forest, rich in endemic plant species, and may support endemic wildlife. The thesis demonstrates the need for rethinking current conceptions in ecosystem management. Biotic linkages and the land uses researched may generate biodiversity benefits and ecosystem services rarely recognized in conservation, science or policy. The results imply that identifying and strengthening essential ecosystem processes could reduce the conflict between biodiversity conservation and societal development in urban and other human dominated landscapes. New avenues can be created that contribute to sustainable use of the human life-support systems.