Introduction
Materials and methods
Tree inventories
City | Total number of trees | Degree of coverage |
---|---|---|
Aarhus | 18,753 | Almost all street trees and 10–15% of park trees have been inventoried |
Copenhagen | 26,032 | Almost all street trees have been inventoried. |
Espoo | 18,067 | 30% of street trees have been inventoried |
Gothenburg | 24,818 | Almost all street trees have been inventoried |
Helsinki | 27,252 | Almost all street trees and 10–15% of park trees have been inventoried. |
Malmö | 54,901 | The inventory is complete for all trees that are maintained by the city’s parks department |
Oslo | 11,756 | The central area of the city has been inventoried |
Stockholm | 13,857 | All street trees in the central area of the city have been inventoried, plus 30% of the trees outside the city centre. |
Tampere | 20,991 | All street trees have been inventoried. |
Turku | 34,180 | 25–30% of the whole urban tree population has been inventoried. |
Total |
250,607
|
Biology and distribution of the longhorned beetle
Tree loss scenarios
Host grade | ALB and CLB feeding and life cycle features | Impact on tree growth | Included in scenario: |
---|---|---|---|
Very good host
| Attracts longhorned beetles. Extensive feeding. Complete life cycle with population or entire tree infestation increases. | Dieback of tree crown and whole tree. | ES, WCS |
Good host
| Moderate feeding. Can complete life cycle. | Dieback of some branches. Dieback of whole tree crown or entire tree if stressed. | WCS |
Host
| Limited feeding by adult beetles. Small number of adults. Slight damaged eggs laid. Can escape attack if nearby trees are more susceptible. | Normal growth with recovery wounds. | WCS |
Resistant or rarely affected
| No feeding activity by adult beetles; no eggs laid. | Normal growth. |
Results
Composition and distribution of urban trees in the 10 major Nordic cities studied
All cities (as a percentage of the total number of trees in all cities) | Aarhus | Copenhagen | Espoo | Gothenburg | Helsinki | Malmö | Oslo | Stockholm | Tampere | Turku | |
---|---|---|---|---|---|---|---|---|---|---|---|
Abies
| 12.16% | ||||||||||
Acer
| 12.34% | 12.13% | 8.34% | 21.10% | 8.24% | 11.96% | 10.03% | 23.27% | 18.82% | 10.16% | 12.79% |
Aesculus
| 2.44% | 2.87% | 3.56% | 4.06% | 4.14% | 5.04% | 3.25% | ||||
Alnus
| 2.12% | 3.94% | 3.54% | ||||||||
Betula
| 10.22% | 4.81% | 2.65% | 10.77% | 9.93% | 10.88% | 2.58% | 11.49% | 8.41% | 38.79% | 13.37% |
Carpinus
| 2.29% | ||||||||||
Crataegus
| 2.00% | 2.56% | 2.23% | 2.52% | 4.20% | 2.01% | |||||
Fagus
| 2.10% | 3.45% | |||||||||
Fraxinus
| 3.22% | 8.03% | 6.73% | 4.04% | 3.25% | 2.36% | 4.84% | 2.91% | |||
Malus
| 2.19% | 2.32% | 2.13% | 3.11% | 2.81% | 3.84% | |||||
Picea
| 6.59% | ||||||||||
Pinus
| 3.08% | 3.61% | 6.14% | 3.51% | 9.99% | ||||||
Platanus
| 2.48% | 9.10% | 2.91% | ||||||||
Populus
| 3.05% | 3.77% | 2.85% | 2.58% | 2.82% | 2.42% | 4.78% | 2.05% | 2.54% | ||
Prunus
| 4.83% | 3.27% | 6.60% | 7.64% | 8.35% | 4.72% | 3.15% | 4.27% | |||
Quercus
| 4.88% | 10.41% | 5.93% | 4.61% | 6.67% | 2.96% | 5.52% | 3.12% | 6.29% | 3.31% | |
Robinia
| 4.51% | ||||||||||
Salix
| 3.62% | 3.18% | 10.34% | 2.42% | 2.97% | ||||||
Sorbus
| 10.41% | 18.91% | 6.71% | 16.49% | 8.05% | 7.57% | 13.10% | 3.05% | 5.74% | 12.57% | 8.13% |
Taxus
| 4.87% | ||||||||||
Tilia
| 21.09% | 15.90% | 25.78% | 22.29% | 21.97% | 43.98% | 12.05% | 27.14% | 23.79% | 23.54% | 10.71% |
Ulmus
| 3.29% | 10.33% | 5.37% | 8.10% | 8.68% | 6.80% | |||||
Less than 2% |
13.34%
|
9.35%
|
10.59%
|
8.21%
|
11.13%
|
7.48%
|
12.48%
|
11.13%
|
6.29%
|
7.48%
|
2.88%
|
All cities (as a percentage of the total number of trees in all cities) | Aarhus | Espoo | Gothenburg | Helsinki | Copenhagen | Malmö | Oslo | Stockholm | Tampere | Turku | |
---|---|---|---|---|---|---|---|---|---|---|---|
Abies | 11.13% | ||||||||||
Acer
| 2.43% | ||||||||||
Acer campestre
| 3.38% | ||||||||||
Acer platanoides
| 8.90% | 8.03% | 20.52% | 3.33% | 10.69% | 4.93% | 2.93% | 18.25% | 16.87% | 9.02% | 11.96% |
Acer pseudoplatanus
| 2.88% | 2.40% | 3.75% | ||||||||
Aesculus hippocastanum
| 2.26% | 2.74% | 3.60% | 3.44% | 3.66% | 4.94% | 3.19% | ||||
Alnus glutinosa
| 3.69% | 3.50% | |||||||||
Betula
| 5.04% | 5.31% | 6.25% | ||||||||
Betula pendula
| 7.69% | 4.10% | 8.26% | 4.23% | 8.98% | 3.76% | 8.19% | 31.94% | 11.16% | ||
Betula pubescens
| 2.40% | 2.07% | |||||||||
Carpinus betulus
| 2.29% | ||||||||||
Fagus sylvatica
| 3.40% | ||||||||||
Fraxinus excelsior
| 2.60% | 7.85% | 2.80% | 4.39% | 2.50% | 2.31% | 4.81% | 2.41% | |||
Picea omorika
| 2.74% | ||||||||||
Pinus sylvestris
| 2.12% | 2.74% | 5.75% | 2.45% | 8.85% | ||||||
Platanus
| 9.10% | ||||||||||
Platanus x hispanica
| 2.44% | 2.79% | |||||||||
Populus tremula
| 2.31% | ||||||||||
Prunus
| 2.33% | 3.39% | |||||||||
Prunus avium
| 4.06% | 4.38% | |||||||||
Quercus petraea
| 2.81% | ||||||||||
Quercus robur
| 3.47% | 7.28% | 4.59% | 3.80% | 2.76% | 2.85% | 3.53% | 6.21% | 3.25% | ||
Robinia pseudoacacia
| 4.25% | ||||||||||
Salix alba
| 2.62% | 3.02% | 9.19% | ||||||||
Sorbus aucuparia
| 3.13% | 2.19% | 9.01% | 3.09% | 11.81% | 3.94% | |||||
Sorbus hybrida
| 2.00% | ||||||||||
Sorbus intermedia
| 4.31% | 5.31% | 5.61% | 5.24% | 2.39% | 3.77% | 8.41% | 3.51% | |||
Sorbus latifolia
| 3.20% | ||||||||||
Sorbus mougeotii
| 6.76% | ||||||||||
Taxus x media
| 4.84% | ||||||||||
Tilia spp.
| 3.59% | 8.16% | 4.08% | 24.45% | 10.09% | ||||||
Tilia cordata
| 5.64% | 2.24% | 2.79% | 3.59% | |||||||
Tilia platyphyllos
| 2.58% | 2.74% | |||||||||
Tilia x europaea
| 14.54% | 7.64% | 19.26% | 10.51% | 39.78% | 18.10% | 7.97% | 8.55% | 21.18% | 9.51% | |
Ulmus glabra
| 2.48% | 9.26% | 2.26% | 7.19% | 7.78% | 5.25% | |||||
Less than 2%
| 43.16 | 25.53% | 18.46% | 39.19% | 21.05% | 37.28% | 45.46% | 23.66% | 23.99% | 13.67% | 27.46% |
Tree loss scenarios
Scenario, beetle species | Percent of total population in all cities | Aarhus | Espoo | Gothen-burg | Helsinki | Copen-hagen | Malmö | Oslo | Stock-holm | Tampere | Turku |
---|---|---|---|---|---|---|---|---|---|---|---|
Expected scenario, ALB | 33% | 27% | 29% | 29% | 32% | 27% | 33% | 42% | 41% | 51% | 30% |
Worst-case scenario, ALB | 77% | 77% | 41% | 79% | 88% | 84% | 81% | 96% | 81% | 92% | 60% |
Expected scenario, CLB | 21% | 31% | 21% | 16% | 20% | 15% | 23% | 20% | 25% | 23% | 21% |
Worst-case scenario, CLB | 62% | 76% | 30% | 62% | 45% | 64% | 72% | 51% | 65% | 71% | 66% |
Expected scenario ALB+ CLB | 45% | 46% | 59% | 37% | 40% | 34% | 47% | 54% | 47% | 64% | 38% |
Worst-case scenario, ALB+ CLB | 94% | 96% | 97% | 92% | 98% | 96% | 96% | 97% | 98% | 97% | 80% |