Ekologisen tiedon hyödyntäminen kaupunkisuunnittelussa

Urbanization leads to irreversible land-use change, which has ecological consequences such as the loss and fragmentation of green areas, and structural and functional changes in terrestrial and aquatic ecosystems. These consequences diminish ecosystem services important for human populations living in urban areas. All this results in a conflict situation: how to simultaneously meet the needs of city growth and the principles of sustainable development, and especially conserve important green areas within and around built-up areas? Urban planners and decisionmakers have an important role in this, since they must use the ecological information mainly from species and biotope inventories and biodiversity impact assessments in determining the conservation values of green areas. The main aim of this thesis was to study the use of ecological information in the urban land-use planning and decisionmaking process in the Helsinki Metropolitan Area, Finland. At first, the literature on ecological-social systems linkages related to urban planning was reviewed. Based on the review, a theoretical and conceptual framework for the research on Finnish urban setting was adapted. Secondly, factors determining the importance and effectiveness of incorporation of ecological information into the urban planning process, and the challenges related to the use of ecological information were studied. Thirdly, the importance and use of Local Ecological Knowledge in urban planning were investigated. Then, factors determining the consideration of urban green areas and related ecological information in political land-use decisionmaking were studied. Finally, in a case study illustrating the above considerations, the importance of urban stream ecosystems in the land-use planning was investigated. This thesis demonstrated that although there are several challenges in using ecological information effectively, it is considered as an increasingly important part of the basic information used in urban planning and decisionmaking process. The basic determinants for this are the recent changes in environmental legislation, but also the increasing appreciation of green areas and their conservation values by all the stakeholders. In addition, Local Ecological Knowledge in its several forms can be a source of ecological information for planners if incorporated effectively into the process. This study also showed that rare or endangered species and biotopes, and related ecological information receive priority in the urban planning process and usually pass through the decisionmaking system. Furthermore, the stream Rekolanoja case indicates that planners and residents see the value of urban stream ecosystem as increasingly important for the local health and social values, such as recreation and stress relief.Kaupungistumisen aiheuttaman maankäytön muutoksen seurauksena viheralueet pirstoontuvat ja niiden pinta-ala vähenee, mikä vuorostaan vähentää kaupunkien asukkaille tärkeiden ekosysteemipalveluiden määrää ja laatua. Tämä kehitys on johtanut ristiriitatilanteeseen: miten voidaan samanaikaisesti ottaa huomioon kaupungin kasvun tarpeet ja kestävän kehityksen periaatteet, sekä erityisesti säästää tärkeät viheralueet rakennetun ympäristön lomassa? Kaupunkisuunnittelijat ja kunnalliset päätöksentekijät ovat tässä avainasemassa, sillä heidän tehtäviinsä kuuluu luontoinventoinneista ja -vaikutusarvioinneista saatavan ekologisen tiedon hyödyntäminen viheralueiden luontoarvojen määrittämisessä, sekä paikallisten asukkaiden, luontoharrastajien ja muiden osallisten tietämyksen ja näkemysten huomioiminen. Tämän väitöskirjan päätavoitteena oli tutkia ekologisen tiedon käyttöä kaupunkisuunnittelussa. Tutkimusalueena oli pääkaupunkiseutu. Erityisesti tutkimuksessa tarkasteltiin a) kuinka tärkeänä ekologista tietoa pidetään suunnitteluprosessissa ja miten se tuodaan prosessiin, b) millainen merkitys ns. paikallisella ekologisella tiedolla on suunnitteluprosessissa, c) mitkä tekijät vaikuttavat viheralueiden ja niihin liittyvän ekologisen tiedon huomioimiseen suunnitteluun liittyvässä poliittisessa päätöksenteossa, ja d) millainen rooli kaupunkialueiden puroekosysteemeillä voi olla kaupunkisuunnittelussa. Päätutkimusmenetelmänä olivat asiantuntijahaastattelut. Väitöskirjatutkimus osoitti että huolimatta ekologisen tiedon käyttöön liittyvistä lukuisista haasteista, nähdään ekologinen tieto yhä tärkeämpänä osana kaavoituksessa ja päätöksenteossa käytettävää kokonaistietopohjaa. Tämä johtuu erityisesti viime vuosina muuttuneesta lainsäädännöstä, mutta myös kaupunkiviheralueiden kasvaneesta yleisestä arvostuksesta. Pääkaupunkiseudulla haastateltujen kaavoittajien, biologien sekä asukas- ja luontoyhdistysten edustajien mukaan myös paikallisen ekologisen tiedon huomioiminen kaavoituksessa on tärkeää, koska se voi täydentää ekologista tutkimustietoa ja osoittaa erityisiä paikallisia luontoarvoja. Tutkimus myös osoitti että harvinaisiin tai uhanalaisiin lajeihin ja elinympäristöihin liittyvä ekologinen tieto on etusijalla myös kaupunkisuunnitteluprosessissa ja läpäisee yleensä koko päätöksentekosysteemin helpommin kuin ns. tavanomaiseen kaupunkiluontoon liittyvä tieto. Lisäksi Rekolanojan tapaustutkimus osoitti että suunnitteluvirkamiesten ja asukkaiden mielestä puroekosysteemin luontoarvot sekä sosiaaliset ja terveyteen liittyvät arvot tulisi ottaa entistä tärkeämpinä huomioon kaupunkisuunnittelussa. Tutkimuksen tuloksia voidaan hyödyntää kaupunkisuunnittelun ja päätöksenteon kehittämisessä

Seasonality in recreation supply and demand in an urban lake ecosystem in Finland

Monetary valuation methods are commonly used to analyze recreation values of water ecosystems. However, most studies on water-related recreation values have not analyzed direct links between ecological elements providing recreation opportunities and user demands. Therefore, we implemented an ecosystem service approach to study human-nature interaction during the actual recreation visit to an urban freshwater site. We developed a conceptual model of local cultural ecosystem services (CES) to study interactions between recreation supply and demand. We were interested in seasonality of water-related recreation supply, and the different demands of summer and off-summer visitors. We chose urban Lake Kuusijärvi in the city of Vantaa, Finland, as our case study area, because it is a popular outdoor recreation area around the year. We identified 14 key elements of the supply of local CES and 22 socio-cultural values for the demand for local CES. We found little seasonal change in recreation supply, but the socio-demographic characteristics and demands of summer and off-summer visitors varied significantly. Demand was higher and more diverse during the summer season, while off-summer visitors were more specific in their demands. Moreover, some visitors feared that some socio-cultural values can be lost if the recreational use of the lake area increases. We discuss our findings in a theoretical context focusing especially on interactions between supply and demand of local CES at Lake Kuusijärvi.peerReviewe

Impacts of urban roadside forest patches on NO2 concentrations

Although it is commonly believed that trees can improve air quality, recent studies have shown that such pollution mitigation can be negligible – or that tree canopies can even increase pollutant concentrations near their sources compared to adjacent treeless areas. We explored the impacts of urban roadside forest patches on the concentrations of nitrogen dioxide in summer and winter in the Helsinki Metropolitan Area, Finland, and especially investigated if canopy cover can result in increased concentrations of NO2 below the canopy. Our results, however, did not show significantly higher – or lower – NO2 concentrations underneath tree canopies compared to levels above canopies. Neither did NO2 levels at the below-canopy sampling height differ significantly between forest patches and adjacent open, treeless areas. The lack of a canopy effect may derive from the rather small size of the forest patches, and – compared to previous studies with similar design – divergent tree species composition forming a dense canopy structure. Our results corroborate previous studies that the potential ecosystem services offered by urban near-road forests are more likely due to benefits other than those related to the removal of air pollutants.Peer reviewe

Quantifying carbon stocks in urban parks under cold climate conditions

Removing CO2 from the atmosphere and storing carbon in vegetation and soil are important ecosystem services provided by urban green space. However, knowledge on the capacity of trees and soils to store carbon in urban parks - especially in the northern latitudes - is scarce. We assessed the amount of organic carbon stored in trees and soil of constructed urban parks under cold climatic conditions in Finland. More specifically, we investigated the effects of management, vegetation type and time since construction on the amount of carbon stored in park trees and soil. We conducted two tree surveys and collected soil samples (0 to 90 cm) in constructed parks managed by the city of Helsinki. The estimated overall carbon density was approximately 130 t per park hectare, when the carbon stock of trees was 22 to 28 t ha-1 and that of soil 104 t ha-1 at the very least. The soil to tree carbon storage ratio varied from 7.1 to 7.5 for vegetated, pervious grounds and from 3.7 to 5.0 for entire park areas. The effects of park management and vegetation type could not be entirely separated in our data, but time was shown to have a distinct, positive effect on tree and soil carbon stocks. The results indicate that park soils can hold remarkable carbon stocks in a cold climate. It also seems that park soil carbon holding capacity largely exceeds that of forested soils in Finland. Preservation and augmentation of carbon stocks in urban parks implies avoidance of drastic tree and soil renovation measures.Peer reviewe

Urban forests near roads do not reduce gaseous air pollutant concentrations but have an impact on particles levels

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Effects of forests on particle number concentrations in near-road environments across three geographic regions

Trees and other vegetation have been advocated as a mitigation measure for urban air pollution mainly due to the fact that they passively filter particles from the air. However, mounting evidence suggests that vegetation may also worsen air quality by slowing the dispersion of pollutants and by producing volatile organic compounds that contribute to formation of ozone and other secondary pollutants. We monitored nanoparticle (>10 nm) counts along distance gradients away from major roads along paired transects across open and forested landscapes in Baltimore (USA), Helsinki (Finland) and Shenyang (China) − i.e. sites in three biomes with different pollution levels − using condensation particle counters. Mean particle number concentrations averaged across all sampling sites were clearly reduced (15 %) by the presence of forest cover only in Helsinki. For Baltimore and Shenyang, levels showed no significant difference between the open and forested transects at any of the sampling distances. This suggests that nanoparticle deposition on trees is often counterbalanced by other factors, including differing flow fields and aerosol processes under varying meteorological conditions. Similarly, consistent differences in high frequency data patterns between the transects were detected only in Helsinki. No correlations between nanoparticle concentrations and solar radiation or local wind speed as affecting nanoparticle abundances were found, but they were to some extent associated with canopy closure. These data add to the accumulating evidence according to which trees do not necessarily improve air quality in near-road environments.Trees and other vegetation have been advocated as a mitigation measure for urban air pollution mainly due to the fact that they passively filter particles from the air. However, mounting evidence suggests that vegetation may also worsen air quality by slowing the dispersion of pollutants and by producing volatile organic compounds that contribute to formation of ozone and other secondary pollutants. We monitored nanoparticle (>10 nm) counts along distance gradients away from major roads along paired transects across open and forested landscapes in Baltimore (USA), Helsinki (Finland) and Shenyang (China) − i.e. sites in three biomes with different pollution levels − using condensation particle counters. Mean particle number concentrations averaged across all sampling sites were clearly reduced (15 %) by the presence of forest cover only in Helsinki. For Baltimore and Shenyang, levels showed no significant difference between the open and forested transects at any of the sampling distances. This suggests that nanoparticle deposition on trees is often counterbalanced by other factors, including differing flow fields and aerosol processes under varying meteorological conditions. Similarly, consistent differences in high frequency data patterns between the transects were detected only in Helsinki. No correlations between nanoparticle concentrations and solar radiation or local wind speed as affecting nanoparticle abundances were found, but they were to some extent associated with canopy closure. These data add to the accumulating evidence according to which trees do not necessarily improve air quality in near-road environments.Peer reviewe

The impact of urban trees on concentrations of PAHs and other gaseous air pollutants in Yanji, northeast China

It is generally conceived that trees can clean polluted air in urban areas sufficiently enough to be considered providers of a vital ecosystem service, although there have not been many field studies showing this in practice in the neighbourhood scale. Using passive sampling methods, we investigated the effect of urban park trees on the concentrations of gaseous polycyclic aromatic hydrocarbons (PAHs), nitrogen dioxide (NO2), ground-level ozone (O3) and sulfur dioxide (SO2) in early summer in the temperate zone city of Yanji, northeast China. Concentrations of total gaseous PAHs and certain PAH constituents were higher and concentrations of O3 lower in tree-covered areas compared to nearby open areas, while tree cover did not affect the concentrations of NO2 and SO2. The higher PAH concentrations under tree canopies may associate with air-soil gas exchange and the trapping of polluted air under canopies. Lower O3 concentrations in tree-covered areas may result from a combination of absorption of O3 by tree canopies, and lower temperatures and solar radiation under tree canopies compared to open areas.Peer reviewe

Greenbelts do not reduce NO2 concentrations in near-road environments

Trees are believed to improve air quality, thus providing an important ecosystem service for urban inhabitants. However, empirical evidence on the beneficial effects of urban vegetation on air quality at the local level and in boreal climatic regions is scarce. We studied the influence of greenbelt-type forest patches on NO2 levels (i) in front of, (ii) inside and (iii) behind greenbelts next to major roads in the Helsinki Metropolitan Area, Finland, during summer and winter using passive collectors. Concentrations of NO2 were significantly higher in front of greenbelts compared to road sides without greenbelts. The more trees there were inside greenbelts the higher the NO2 level in front of greenbelts, likely due to the formation of a recirculation zone of air flow in front of greenbelts. Similarly, NO2 levels were higher inside greenbelts than in open areas without them, likely due to reduced air flow inside greenbelts. NO2 levels behind greenbelts were similar to those detected at the same distance from the road but without greenbelts. Our results suggest that, regardless of season, roadside greenbelts of mostly broadleaf trees do not reduce NO2 levels in near-road environments, but can result in higher NO2 levels in front of and inside greenbelts.Trees are believed to improve air quality, thus providing an important ecosystem service for urban inhabitants. However, empirical evidence on the beneficial effects of urban vegetation on air quality at the local level and in boreal climatic regions is scarce. We studied the influence of greenbelt-type forest patches on NO2 levels (i) in front of, (ii) inside and (iii) behind greenbelts next to major roads in the Helsinki Metropolitan Area, Finland, during summer and winter using passive collectors. Concentrations of NO2 were significantly higher in front of greenbelts compared to road sides without greenbelts. The more trees there were inside greenbelts the higher the NO2 level in front of greenbelts, likely due to the formation of a recirculation zone of air flow in front of greenbelts. Similarly, NO2 levels were higher inside greenbelts than in open areas without them, likely due to reduced air flow inside greenbelts. NO2 levels behind greenbelts were similar to those detected at the same distance from the road but without greenbelts. Our results suggest that, regardless of season, roadside greenbelts of mostly broadleaf trees do not reduce NO2 levels in near-road environments, but can result in higher NO2 levels in front of and inside greenbelts.Peer reviewe

Gaseous polycyclic aromatic hydrocarbon concentrations are higher in urban forests than adjacent open areas during summer but not in winter – Exploratory study

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