The performance of city trees

Trees are often the largest components of landscape greenery, and can help enhance the environmental quality of city landscapes. For example, trees can lower temperatures by providing shade, and reduce the risk of flooding by intercepting rainfall. Such benefits accumulate across wider areas, producing substantial effects that can help make cities more liveable and adaptable to climate change. Trees are thus a form of ‘natural capital’ that produce value for people.

Tree species within benefit–cost assessments performed worldwide. Figure from Song et al. (2018).

Many cities have started to assess the status and health of these natural capital assets, which is an important step to incorporate the environment into holistic, national-scale planning. The downstream effects associated with trees often rely on their size and structure, which varies between species and changes over time. For practical purposes, however, measuring these multiple dimensions is usually not possible. Such values may have to be estimated indirectly using allometric relationships between the quantities of interest and easily-measured parameters such as a tree’s trunk diameter.

Street trees in Singapore (a-c) mapped according to summarised metrics within hexagonal regions, and (d) mapped individually according to the extent that they are abnormally taller/shorter than predicted by their measured diameter. Figure from Song et al. (2020).

As part of my PhD work, I developed the R package allometree to build such allometric relationships, as well as a prototype web application demonstrating how the package may be used. If you’re interested, you may check out the following publication:

Song, X. P., Lai, H. R., Wijedasa, L. S., Tan, P. Y., Edwards, P. J., Richards, D. R. (2020), Height–diameter allometry for the management of city trees in the tropics. Environmental Research Letters, 15, 114017. https://doi.org/10.1088/1748-9326/abbbad

Rapid advances in remote sensing may soon reduce the manual effort required for data collection, and shift research and development toward real-time monitoring for tree management. However, systems and workflows will need to evolve to take advantage of such innovations. Work is needed to streamline data pipelines for analyses, and to integrate multiple datasets and objectives effectively for decision-making.

Examples showing (a) key inputs required for urban tree management, and (b) data sources that can supplement inventory data for urban tree management. Figure from Song et al. (2020).

References

• Song, X. P., Lai, H. R., Wijedasa, L. S., Tan, P. Y., Edwards, P. J., Richards, D. R. (2020), Height–diameter allometry for the management of city trees in the tropics. Environmental Research Letters, 15, 114017. https://doi.org/10.1088/1748-9326/abbbad

• Song, X. P., Tan, P. Y., Edwards, P. J., Richards, D. R. (2018). The economic benefits and costs of trees in urban forest stewardship: A systematic review. Urban Forestry & Urban Greening, 29, 162–170. https://doi.org/10.1016/j.ufug.2017.11.017

• Song, X. P., Richards, D. R., Edwards, P. J., Tan, P. Y. (2017). Benefits of trees in tropical cities. Science, 356 (634), 1241. https://doi.org/10.1126/science.aan6642

Citation

BibTeX citation:

@article{x. p.2020,
  author = {X. P. , Song and H. R. , Lai and L. S. , Wijedasa and P. Y.
    , Tan and P. J. , Edwards and D. R. , Richards},
  title = {Height–Diameter Allometry for the Management of City Trees in
    the Tropics},
  journal = {Environmental Research Letters},
  volume = {15},
  pages = {114017},
  date = {2020},
  url = {https://xpsong.com/posts/street-trees},
  doi = {10.1088/1748-9326/abbbad},
  langid = {en}
}

For attribution, please cite this work as:

X. P., Song, Lai H. R., Wijedasa L. S., Tan P. Y., Edwards P. J., and Richards D. R. 2020. “Height–Diameter Allometry for the Management of City Trees in the Tropics.” Environmental Research Letters 15: 114017. https://doi.org/10.1088/1748-9326/abbbad.