ANALYSIS: More “deep soil” for Brisbane multi-unit res development. So what?

Future Brisbane Blueprint proposes an increase in “deep planting” areas on multi-unit residential sites from 10 to 15% of site area across Brisbane. What difference can 5% more site area for deep planting make to Inner City Brisbane tree cover on multiunit residential sites?

Answer =         an estimated additional 20,000 m2 of tree canopy per year (by 2031), which

  • adds summer cooling benefits to Brisbane’s most populated urban hot spot
  • grows Inner Brisbane’s canopy area from 16.3% by an extra 0.1 % per year **
  • sequesters extra 10 tonnes/yr of carbon dioxide, delivering the equivalent of almost 560,000 less kilometres of passenger car trips or 40 less passenger cars in greenhouse gas emission equivalents(GGE)
  • intercepts extra 110 kg of air pollutants/yr, (mostly particulate matter PM10 and PM2.5)
  • intercepts extra 800,000 litres of rainfall/yr

Estimate calculations:

INNER CITY BRISBANE“other residential” (non house) building approvals*Number of apartments completed#Site area of approved or completed multiunit dwellings10% site area of approved or completed multiunit dwellings15% site area of approved or completed multiunit dwellingsPotential tree canopy area in 2031 for 10% deep planting##Potential tree canopy area in 2031 for 15% deep planting##
2017-20183,3384,275100,000m2###10,000 m215,000 m240,000 m260,000 m2


*Australian Bureau Statistics 8731.0 Building Approval SA2 scale

# BIS Oxford Economics forecast for whole of Brisbane published in “The Urban Developer”, assuming 75% of completions in Inner City Brisbane

## Based on deep planting area(DPA) X assumed available 1m depth within DPA, converted to tree canopy area using Leake & Haege “Soil volume simulator”  in reverse.

### Based on estimate of 25 m2 site area per completed apartment 2017-2018

** Based on Inner Brisbane land area of 8,000 ha and 2014 tree cover of 16.3 % (or 1,304 ha) reported in Jacobs, B., Mikhailovich, N., and Delaney, C. (2014) Benchmarking Australia’s Urban Tree Canopy: An i-Tree Assessment, prepared for Horticulture Australia Limited by the Institute for Sustainable Futures, University of Technology Sydney.