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The future of urban trees – assessing the potential impact of climate change on urban tree populations in two European cities

Elverich, Pia LU (2021) In Student thesis series INES NGEM01 20211
Dept of Physical Geography and Ecosystem Science
Abstract
Due to climate change, cities are increasingly facing the situation of being exposed to more frequent and prolonged extreme weather events in the future, such as heat and droughts, which are exacerbated by urban heat island (UHI) effects. The implementation of green infrastructure (GI) in the form of trees is seen as a possible adaptation measure to regulate the microclimate. However, there is an increased risk that both existing and future urban tree populations will suffer significantly from changing climate conditions.
The aim of this study was to assess to what extent the current tree population in Berlin and Vienna will be threatened by heat and drought periods in the future and to what extent adaptation measures might become... (More)
Due to climate change, cities are increasingly facing the situation of being exposed to more frequent and prolonged extreme weather events in the future, such as heat and droughts, which are exacerbated by urban heat island (UHI) effects. The implementation of green infrastructure (GI) in the form of trees is seen as a possible adaptation measure to regulate the microclimate. However, there is an increased risk that both existing and future urban tree populations will suffer significantly from changing climate conditions.
The aim of this study was to assess to what extent the current tree population in Berlin and Vienna will be threatened by heat and drought periods in the future and to what extent adaptation measures might become necessary. To this end, future climate-related heat and drought threats were investigated based on two emission scenarios (RCP 4.5, RCP 8.5) and selected climate indicators for both the near future (2021-2050) and the distant future (2071-2100). The heat and drought tolerance of trees was assessed based on a literature review. In addition, the exposure of categorised trees in relation to UHI effects was investigated to identify particularly vulnerable locations and recurring patterns.
The risk of extreme events (heat and drought) was found to increase in the future for both climate scenarios studied for both cities, especially in the distant future and at the beginning and end of the growing season. Of the urban tree species studied, the majority were classified as moderately sensitive and moderately tolerant. The distribution of highly sensitive trees within the city showed similar distribution patterns in the two cities with single hotspots in parks but different average UHI intensity exposures. It can be concluded that timely, targeted planning of GI adaptation measures is already essential for both cities to be able to provide adequate GI in the near, but especially in the distant future. (Less)
Popular Abstract
Climate change will expose cities to more frequent and prolonged extreme weather events such as heat waves and droughts. The impacts are exacerbated in urban areas by urban heat island effects, which lead to even higher temperatures inside cities compared to more natural environments outside the city. Very high temperatures can lead to health problems for the population in addition to a general reduction in the quality of life. To reduce these bad consequences, one possible measure in affected cities is the expansion and planting of trees. This is because trees help to cool the environment through their shade and by cooling the air through transpiration. Unfortunately, due to the changing climatic conditions, there is an increased risk... (More)
Climate change will expose cities to more frequent and prolonged extreme weather events such as heat waves and droughts. The impacts are exacerbated in urban areas by urban heat island effects, which lead to even higher temperatures inside cities compared to more natural environments outside the city. Very high temperatures can lead to health problems for the population in addition to a general reduction in the quality of life. To reduce these bad consequences, one possible measure in affected cities is the expansion and planting of trees. This is because trees help to cool the environment through their shade and by cooling the air through transpiration. Unfortunately, due to the changing climatic conditions, there is an increased risk that both existing and future urban trees will suffer significantly from the changing climatic conditions. To find out to what extent the most common tree species in Berlin and Vienna could be threatened by heat and drought periods in the future, as well as urban heat island effects, and to what extent supporting measures will be necessary, this study investigated. The exact development of the climate depends strongly on today's decisions regarding greenhouse gas emissions. Thus, there are several possible climate developments. In this study, two possible scenarios were investigated. Since trees contribute more to the cooling of the environment when they are older and larger, they need to be planted in time to fulfil their full potential. Therefore, it was investigated whether different trees are generally tolerant to heat and drought and whether they will already be endangered due to the climate in the next decades or rather at the end of the century, to deduce whether new trees already need to be planted. Both future climates studied clearly showed that there will be more and longer heat and dry periods in both cities and that the less tolerant species will be exposed to higher risks. The results show that timely, targeted planning of tree structure is already essential for both cities to benefit from the positive effects of trees in the near, but especially in the distant future. (Less)
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author
Elverich, Pia LU
supervisor
organization
course
NGEM01 20211
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Physical geography, ecosystem analysis, climate adaptation, urban trees, green infrastructure, urban heat island effect, ecosystem services
publication/series
Student thesis series INES
report number
542
language
English
id
9058009
date added to LUP
2021-06-23 12:04:05
date last changed
2021-06-23 12:04:05
@misc{9058009,
  abstract     = {{Due to climate change, cities are increasingly facing the situation of being exposed to more frequent and prolonged extreme weather events in the future, such as heat and droughts, which are exacerbated by urban heat island (UHI) effects. The implementation of green infrastructure (GI) in the form of trees is seen as a possible adaptation measure to regulate the microclimate. However, there is an increased risk that both existing and future urban tree populations will suffer significantly from changing climate conditions. 
The aim of this study was to assess to what extent the current tree population in Berlin and Vienna will be threatened by heat and drought periods in the future and to what extent adaptation measures might become necessary. To this end, future climate-related heat and drought threats were investigated based on two emission scenarios (RCP 4.5, RCP 8.5) and selected climate indicators for both the near future (2021-2050) and the distant future (2071-2100). The heat and drought tolerance of trees was assessed based on a literature review. In addition, the exposure of categorised trees in relation to UHI effects was investigated to identify particularly vulnerable locations and recurring patterns. 
The risk of extreme events (heat and drought) was found to increase in the future for both climate scenarios studied for both cities, especially in the distant future and at the beginning and end of the growing season. Of the urban tree species studied, the majority were classified as moderately sensitive and moderately tolerant. The distribution of highly sensitive trees within the city showed similar distribution patterns in the two cities with single hotspots in parks but different average UHI intensity exposures. It can be concluded that timely, targeted planning of GI adaptation measures is already essential for both cities to be able to provide adequate GI in the near, but especially in the distant future.}},
  author       = {{Elverich, Pia}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Student thesis series INES}},
  title        = {{The future of urban trees – assessing the potential impact of climate change on urban tree populations in two European cities}},
  year         = {{2021}},
}