Facing Climate Change: Urban Gardening and Sustainable …
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7. Quality of wood: Once the trees reach the age known to them, the municipality
may resort to re-culture, and in rare cases may require digging out trees. In these
cases, wood quality is required.
8. No Street Tree is Perfect: There is no such thing as the street tree that will fulfil
perfectly all aspects of our selection criteria.
9. Root system characteristics: Trees species which do not have a history of
problematic root behaviour are preferred.
10. Branch drop and windthrow: Choose trees which are not known for unexpected
branch drop, or likely to blow over in strong winds.
11. Deciduous versus evergreen: The requirement for summer shade and winter sun
should be factored into the selection process.
12. Non-grafted cultivars: carefully consider if a grafted species has been shortlisted. When suffering hardship, grafted specimens can shoot from the understock, creating a maintenance burden.
13. Fruit production: Apart from potential weed production from fruit, fleshy or
woody fruit can create a hazard when they fall on pavements.
14. Habitat linking: strategic location of particular indigenous tree species to link
fragmented habitat or continue a wildlife corridor, can be important to some
classes and populations of animals. This must be considered on a site-by-site
basis.
11.1 Big or Tall Trees
Tree planting and plantation urban forestry are well established both in the private
and public sectors. The data released by the UN’s Food and Agriculture Organisation
suggest that plantation forests comprised an estimated 7% of global forest area in
2010 [137]. Trees are also planted as part of efforts to restore natural forests as well
as in agroforestry, which involves increasing tree cover on urban and agricultural
lands.
– Under certain conditions plantations can grow relatively fast, thus absorbing CO 2
at higher rates. In the absence of major disturbances, newly planted or regenerating
forests can continue to absorb carbon for 20–50 years or more. Tree planting could
sequester (remove from the atmosphere) around 1.1–1.6 GT of CO 2 per year (that
compares to total global greenhouse gas emissions equivalent to 50 GT of CO 2 .
– Tree planting and afforestation were included as activities eligible for finance
under the Kyoto protocol. Kyoto’s rules and procedures, however, restricted the
scale and scope of these activities. As a result, projects have struggled to get off
the ground and the carbon sequestered has been almost negligible.
– Dense, spreading species—the classic shade trees such as Ficus retusa, F. benghalensis, Delonix regia, and Cassia nodosa don’t work well in the forest garden
because they cast deep shadows over a large area. Better choices are F. religiosa,
Khaya senegalensis, and Bauhinia variegatum.
379
7. Quality of wood: Once the trees reach the age known to them, the municipality
may resort to re-culture, and in rare cases may require digging out trees. In these
cases, wood quality is required.
8. No Street Tree is Perfect: There is no such thing as the street tree that will fulfil
perfectly all aspects of our selection criteria.
9. Root system characteristics: Trees species which do not have a history of
problematic root behaviour are preferred.
10. Branch drop and windthrow: Choose trees which are not known for unexpected
branch drop, or likely to blow over in strong winds.
11. Deciduous versus evergreen: The requirement for summer shade and winter sun
should be factored into the selection process.
12. Non-grafted cultivars: carefully consider if a grafted species has been shortlisted. When suffering hardship, grafted specimens can shoot from the understock, creating a maintenance burden.
13. Fruit production: Apart from potential weed production from fruit, fleshy or
woody fruit can create a hazard when they fall on pavements.
14. Habitat linking: strategic location of particular indigenous tree species to link
fragmented habitat or continue a wildlife corridor, can be important to some
classes and populations of animals. This must be considered on a site-by-site
basis.
11.1 Big or Tall Trees
Tree planting and plantation urban forestry are well established both in the private
and public sectors. The data released by the UN’s Food and Agriculture Organisation
suggest that plantation forests comprised an estimated 7% of global forest area in
2010 [137]. Trees are also planted as part of efforts to restore natural forests as well
as in agroforestry, which involves increasing tree cover on urban and agricultural
lands.
– Under certain conditions plantations can grow relatively fast, thus absorbing CO 2
at higher rates. In the absence of major disturbances, newly planted or regenerating
forests can continue to absorb carbon for 20–50 years or more. Tree planting could
sequester (remove from the atmosphere) around 1.1–1.6 GT of CO 2 per year (that
compares to total global greenhouse gas emissions equivalent to 50 GT of CO 2 .
– Tree planting and afforestation were included as activities eligible for finance
under the Kyoto protocol. Kyoto’s rules and procedures, however, restricted the
scale and scope of these activities. As a result, projects have struggled to get off
the ground and the carbon sequestered has been almost negligible.
– Dense, spreading species—the classic shade trees such as Ficus retusa, F. benghalensis, Delonix regia, and Cassia nodosa don’t work well in the forest garden
because they cast deep shadows over a large area. Better choices are F. religiosa,
Khaya senegalensis, and Bauhinia variegatum.