The Sustainable Garden - No.2 - Sustainability and your garden

What has sustainability got to do with gardens? and aren’t gardens always green anyway? For years many have sought to highlight the link between gardens and the environment but what does that mean for us in practice?

It is easy to imagine that the small space outside your house couldn’t possibly make any difference one way or the other.

But when you consider that the combined area of all gardens in the UK is more than 25 times bigger than the largest nature reserve (The Great Trossachs Forest) and about the same size as the biggest national park (The Cairngorms) you can see their potential.

The difference between paving a combined total of either 20% or 10% of our national garden area is the difference between producing many millions of tonnes of additional carbon emissions and creating a new nature reserve twice the size of the Great Trossach Forest (see calculation below).

It’s evident therefore that our gardens have the potential to make a real difference when it comes to tackling both climate change and habitat loss.

The truth is though it’s hard to determine exactly how ’green’ the UK’s gardens actually are. They just vary so much and there is a complex array of interactions at play.

We do know that plants and soil absorb carbon and that the materials we use in the garden have a carbon cost. We know that large areas of paving can contribute to urban heating and flooding. We know that well planted gardens can contribute to urban cooling, provide habitat for wildlife and be beneficial to human health. We know that lawns, which make up 60% on average of our gardens, have a relatively high carbon cost and low ecological benefit.

Less clear is the balance, mix and proportion of all these positives and negatives. However, what we can say is that at their best gardens can be carbon neutral ecological hotspots and at their worst mini environmental disasters. The aim therefore is about shifting the dial towards the positive.

Sustainability is a term that has become associated with everything from fashion to food, but its use, or overuse and even abuse (greenwash), shouldn’t invalidate its meaning.

In 1987 the term ‘sustainable development’ was given to mean development that ‘meets the needs of the present without compromising the ability of future generations to meet their own needs’. That still seems a pretty good definition.

Since then the concept has reached the heart of government policy and every corner of society. In 2008 the Climate Change Act became law and each year the UK’s commitment to cut carbon emissions intensifies, at least in word.

The world of landscape design and gardens is no exception. The Landscape Institute, the body which represents landscape architects, is explicit in its position and committed to galvanising its profession to take action and ‘deliver effective, sustainable climate solutions’.

As far back as 2002 the Royal Horticultural Society (RHS), along with others, published a report ‘Gardening in a Global Greenhouse’. This was updated in 2017 as ‘Gardening in a Changing Climate’ and provides a detailed assessment of how gardens can be adapted both to continue to thrive and also to provide important services such as carbon capture and flood alleviation.

So, what does sustainability mean when it comes to designing our gardens?

The description used by the Association of Professional Landscape Designers (APLD) in the US is a great place to start. It essentially highlights two key aspects – energy and habitat – minimizing the one while maximising the other.

Energy: there is an energy cost to every action we take in the garden, and with that a corresponding carbon cost (which we know is the principle cause of climate change). Energy is used in the extraction, processing and transport of the materials we use such as paving and timber. Energy is used during the installation of those materials by your landscape contractor. There is also an energy cost to the use of mains water, mowing the lawn and cutting the hedge. Obviously the suggestion is not that we should cut out all those materials or activities, but rather be aware of the true cost, consider how to be more efficient and mindful of their conservation so that, as the APLD puts it, ‘future generations will have options for the use of those resources’.

Habitat: Landscapes, both here in the UK and abroad, continue to be exploited and developed, and the space available for ‘nature’ to function and wildlife to inhabit shrinks. The pressure on ecosystems and thousands of species is, to put it mildly, intense. It may not be possible for gardens to replace large scale landscapes where big beasts roam but habitats function on many different scales and both collectively and individually gardens can provide a significant piece of the jigsaw. Bearing this mind when we design our gardens will give space for a wide range of plants and animals.

Put simply therefore, at the heart of the environmental predicament we find ourselves in is the consumption of resources and erosion of natural habitats that goes beyond what the Earth’s systems can sustain. And it is those systems that ultimately sustain us.

Striving for sustainability is about trying to redress the environmental balance, allowing some give as well as take. Minimizing the negative impacts of our actions and maximizing the positive ones. It is about our gardens being part of the solution not part of the problem.

Beyond the energy and the habitat described above, sustainable landscapes and gardens are sometimes described in terms such as ‘green infrastructure’ and ‘ecosystem services’. These are important concepts, and useful to have some understanding of, but very broadly, they allude to the array of interactions our gardens have with the world beyond the fence.

It is helpful therefore to view our gardens not in isolation but as part of a bigger picture. Asking ourselves the question not just ‘if everybody did what we are doing, what impact would that have’? but ‘how can my garden help?’. A classic current example is how small domestic gardens, en masse, can help alleviate urban flooding.

Is there any room for compromise? Judging what is or what isn’t sustainable is not always straight forward. So yes, the odd compromise along the way is likely - however, the threshold of what we are prepared to accept can and should be raised.

All this doesn’t mean we have to give up on the idea of a nice garden, just do nothing and simply turn it over to nature. Good design, a little shift in attitude and being open to new ideas and mindful of our actions will help ensure the garden can still be a place that satisfies our needs - how it looks, what we want to use it for, the time and money we can afford to devote to it.

A beautiful, stylish and modern garden can still be the aim and is very much achievable. Hopefully over the coming weeks you will see how.

* This calculation is for illustration purposes only.

The total area of gardens in the UK is estimated to be 433,000 hectares. 10% of that is 43,000 hectares, or 430 million square metres.

The carbon emission associated with the manufacture of paving can vary considerably but a quick search online will reveal anything from 14kg to 47kg per square metre.

Taking a mid-point of 30.5kg per sqm and applying that to an area equivalent to 10% of the UK's garden area (i.e. 43,000 hectares) would amount to 13,115,000 tonnes of CO2 produced (The UK's total CO2 emissions in 2018 were 364 million tonnes).

By comparison, reducing paving in UK gardens by an area equivalent to 10% of the national garden area would provide an area of 43,000 hectares for carbon neutral use, or even carbon negative use such as planting. An area 2.6 times bigger than the Great Trossachs Forest.

Next time - 'Through dark green eyes - looking at our gardens differently'