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Finally, the weather is starting to cool down here, in South East Queensland Australia!
Plants use cues from the weather and climate to time their growth, flowering and fruiting. But as the world heats up due to climate change, these patterns are changing.
So how is climate change affecting our gardens, and what can we do about it?
Many temperate plants have evolved to reproduce in spring to avoid damage from extreme cold or heat. Warmer conditions tend to speed up these processes, causing plants to grow faster.
Plants have evolved sophisticated mechanisms to synchronize climate. This means they are excellent bio-indicators of climate change.
In Australia, plants in southern Australia are maturing earlier – winegrapes, for instance, by 27 days on average between 1999 and 2007. We can see this in wine growers’ records.
Other plants may behave differently. Fruit trees such as apples need cold weather to break buds from their dormant state, before commencing growth when warm temperatures arrive.
This means after warm winters, such as this one, flowering may actually be delayed.
The earlier emergence of reproductive tissues may increase the risk of devastating frost damage. Contrary to what you might expect, evidence shows recent warming in southern Australia has not necessarily led to fewer frosts.
On the other hand, plants that delay flowering because of warmer winters may reduce their frost risk.
Shifts in flowering timing, earlier or later, can be problematic for plants that rely on pollination between different varieties. Both varieties must shift flowering in the same way for flowering periods to overlap.
If flowering times don’t overlap, pollination will be less successful, producing fewer fruit.
Bee and bird pollinators must also adjust their activity in sync with changes to flowering time to facilitate pollination.
Faster maturity may shift ripening into hotter times of year, as seen for wine grapes. This increases the risk of extreme heat damage.
Pests and diseases will also adjust their growth cycles in response to a changing climate. One pest well known to gardeners is the Queensland Fruit Fly (QFF). Their maggots are found in a wide range of fruits.
Climate change will likely favour fruit flies. Warmer temperatures for longer periods will encourage a higher number of generations each year. Meanwhile, reduced cold weather will mean fewer fruit flies will die, increasing the flies’ survival rates.
On the other hand, temperate pests and diseases may decrease if warming exceeds their temperature thresholds.
What have you observed? Citizen scientists who track the timing of biological events have provided valuable information, especially in Australia, for us to monitor and interpret plant responses to climate change.
Keeping garden records will show if and how your plants or pests are changing their patterns.
If you observe your flowers emerging earlier, coverings can be used to protect against frost. Keep an eye on cross-pollinators – are they flowering together? If not, consider planting a different cross-pollinator.
Nets are an effective way to reduce heat damage and can also be used to protect against some pests. Setting pest traps according to weather rather than the calendar will help disrupt the first generation and reduce pest impact.
Climate change has already influenced biological responses, perhaps even in your own garden. Seeing these changes in our gardens gives us an insight into the significant challenges faced by our food production systems under a changing climate.
Adapting to current and future climate change is a reality, and is essential to preserve both the enjoyment we experience in our own gardens and the security of future food supply.
We have talked about how the changing climate effects our gardens in general but last winter in Queensland we had floods.
In recent years, there seems to have been a rise in the extreme weather all over the world from terrible flooding in Bangladesh and Pakistan, the record cold snap in North America, to one of the wettest winters on record in the UK.
Extreme events are very difficult to tackle, and in some cases there is little we can do, other than increase our preparedness and our recovery response. However there is one thing we can do in response to smaller scale, more common events such as flooding from intensive rain showers. As winter closes in on, it’s worth looking at some of the ways we can better manage excess water.
People have tackled floods for centuries, but modern urban development has thrown up a set of new challenges. The more we develop the landscape, the more rainwater stays on the surface rather than sinking into the soil. That means water gets onto the roads and into drains more quickly, bypassing some aspects of the natural hydrological cycle.
Rooftop plants (including green-roofs and roofgardens) along with rainwater collectors and rain gardens can help slow things down and spread the impact of heavy rain out over a longer period. The idea is to replace some of the trees, grass, hollows and wetlands that have been lost to concrete, and so mimic a more natural flow of water.
One approach that aims to manage rainwater more naturally is known as Sustainable Urban Drainage Systems (SUDS). SUDS are particularly useful in helping to manage small but frequent floods from rainfall, just as the un-urbanised landscape would.
The system has three main aims: to catch and slow down the flow of water; to improve the quality of water by capturing and treating the pollutants it contains; and to benefit the local community by providing a green space that people can enjoy and where wildlife can flourish.
Managing water where it lands – at its source – is one of the most effective ways of reducing runoff. We can do this by creating green roofs and raingardens, for example, as well as by designing other mechanisms that slow down the flow of rainwater from our roads, roofs and driveways.
Sometimes it rains so heavily that no sensible drainage system could handle the flow. Where serious and sustained flooding is caused by unprecedented rain – as happened in the UK last winter – it has to be said that these small-scale systems are less effective.
Sustainable drainage measures would probably have helped initially, but no form of water management could have accommodated rainfall on that scale.
Record-breaking rainfalls combined with high tides and high water tables presented us with a perfect combination of conditions that any traditional engineering would have been hard pressed to tackle.
In these cases, we need to think about how to be more resilient to floods – how we can be more prepared, reduce the impact of the flood, and recover more quickly.
Researchers in the UK have been working on this for some time now, and in some cases such approaches have become law – in Scotland, for instance, all new developments since 2006 must have sustainable drainage.
And who doesn’t love a rooftop garden?
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