Metropolitan Melbourne Investigation - Victorian Environmental ...

4
IMPLICATIONS
OF CLIMATE
CHANGE FOR PUBLIC LAND
The evidence is increasingly clear that the earth is
experiencing a period of rapid warming associated with
increased levels of greenhouse gases. Discussion and
research continue around the details of future climate
change scenarios based on modelling. These discussions
relate to the magnitude of change for specific levels of
greenhouse gases and not the basic premise that climate
change is occurring.
Some uncertainties will continue given the complexity
of the climate system and the range of possible future
greenhouse gas emissions scenarios. Accordingly, many
uncertainties surround projections of the risks that climate
change poses, especially at finer spatial scales, and how
communities and natural systems will be affected by, and
respond to, these changes. 14
Climate change is likely to impact on Melbourne’s public
land through increasing mean temperatures, greater
rainfall variability (ranging from drought to heavy rainfall
events), greater bushfire risk, pressures on biodiversity,
and coastal inundation from storm surges combined with
sea level rise. These environmental changes will in turn
impact on Melbourne’s liveability and natural values.
Section 2.4 of the discussion paper described
Melbourne’s climate and the projected climate changes.
Chapter 7 of the discussion paper considered the
predicted impacts of this changing climate on public land,
with an emphasis on how these will affect Melbourne’s
liveability and natural values, and discussed the role that
public land can play in mitigating and adapting to the
impacts of climate change. The pressures on biodiversity
from climate change were also discussed in chapter 8 of
the discussion paper.
This chapter of the final report summarises and updates
the information provided in the discussion paper on
climate change and public land with a further discussion of
some issues. Readers are encouraged to also refer to the
discussion paper.
4.1 Increasing temperatures
and rainfall variability
Globally, 2010 was one of the warmest years on record
occurring at the end of the warmest decade recorded
since 1880. The global mean annual temperature has now
been above average each year for the last 25 years. 15 In
Australia, mean temperatures were not as high as global
mean temperatures, but were none-the-less significantly
above the long-term average for both mean minimums
and maximums, with the last decade also the warmest ten
year period on record. 16
Although Melbourne has experienced a relatively wet
2011 so far, it is uncertain if this reflects a long-term shift
back to more historical rainfall patterns. The severe rainfall
shortages over the preceding decade may reflect a stepdown
reduction to a lower long-term average; however
further research is needed to improve our understanding
between climate change and the climatic processes that
influence rainfall.
4.1.1 Countering urban heat islands
Chapter 7 of the discussion paper described how urban
heat islands are caused by hard impermeable surfaces
(such as roads, footpaths and roofs) absorbing heat
during the day and slowly releasing it during the night. 17
It also discussed how parks and other treed areas and
water bodies can help counter this effect. The importance
of vegetated public land for ameliorating the urban heat
island effect is likely to increase as urban densification
increases in Melbourne and the climate warms.
Numerous submissions responding to the discussion
paper commented on the importance of retaining
vegetation on public land to reduce the urban heat island
effect (see box 4.1), provide biodiversity corridors and
contribute more generally to Melbourne’s liveability. Several
submissions stressed the importance of trees on public
land, such as nature strips, parks and wildlife corridors
along rail and road reserves. The “boundary to boundary”
development of housing blocks, and the subsequent
reduction in private trees and gardens, was one of the
reasons cited as making urban forests on public land
even more important. Some submissions called for the
protection of existing urban vegetation, particularly native
vegetation, and for the planting of more trees in urban
26