Blue-Green vs. Grey-Black Infrastructure – Which is best for C21st survival?

By Peter Bridgewater, McKinnon-Walker Fellow

As we moved towards the end of the second decade of the C21st it is clear we are in the era of the Anthropocene –even if geologists are still undecided when – or even if – there is such a thing.  Irrespective of the geologists we are certainly in a different era from even 50 years ago, and this necessitates a different way of thinking and viewing our environments, from the wild to the urban…

But what does living in the Anthropocene really mean?  It means:

  • living with relentless global change;
  • probing, even exceeding, “planetary boundaries”;
  • witnessing homogenisation of biodiversity and cultural diversity;
  • landscapes subject to significant hydrological change;
  • significant increases in regular and episodic pollution events.

In such a world, ecosystem service provision will decrease, while at the same time people’s need for those services will increase. Ecosystem resilience will also decrease, as disturbances and rapid change increase.  This change has arisen as people have become the strongest driver in ecosystem change, and yet our knowledge of ecosystems remains limited.

The dilemmas of this situation are well-summarised by Purdy (2015) with an addition from me:

“Climate [Global] change is planetary engineering without design. These facts of the Anthropocene are scientific, but its shape and meaning are questions for politics—a politics that does not yet exist.”   In this quote Purdy draws attention to the need not only for a scientific understanding of the Anthropocene, but also a need to understand the political and socio-cultural dimensions of what is happening.  One way to address these issues is to look at the different kinds of infrastructure that are present, or can be developed, in our urban and rural areas.

We are all familiar with the grey infrastructure of roads, rail, electricity easements, sometimes concrete “trained” streams and creeks.  But there is also green and blue infrastructure.  Green Infrastructure is a tool for providing ecological, economic, cultural and social benefits through nature-based solutions, typically in an urban or peri-urban environment.  Green Infrastructure is a network of semi-natural areas, novel ecosystems and green space that delivers ecosystem goods, services and benefits that underpin human well-being and quality of life.   The application of green infrastructure been greatest in Europe, North America, Australia and New Zealand.  In Europe, the EU Biodiversity Strategy aims to ensure that “by 2020, ecosystems and their services are maintained and enhanced by establishing green infrastructure and restoring at least 15% of degraded ecosystems”.

But it’s not just Europe; Asian countries including China, Japan, Republic of Korea, and Singapore are looking to use green infrastructure in revitalising existing cities, and in designing new cities e.g. Sino-Singapore Tianjin Eco-City, Guiyang Eco-City, both currently under development.

Green infrastructure, however, is relatively new concept that needs quantitative analysis and indicators of success. Policy makers struggle to understand how green infrastructure can be integrated into policy development and implementation.   Some easily quantified green infrastructure e.g. ecoducts, natural water management systems, and green roofs, tend to have clear functions, and indicators exist to assess their performance. Wet areas, including open water in green infrastructure, are sometimes called blue infrastructure. In any urban area, the sum of green and blue infrastructure 
contributes habitat for wild flora and fauna, and offers linkage from urban through peri-urban to “rurban” space for wildlife, as well as improving the human experience. In general, blue-green infrastructure has “multifunctional potential” – being able to fulfil multiple functions at the same time.

Blue-green infrastructure gives rise to the idea of the three “c” s – Continuum, Connectivity, and Conservation. Continuum because there should be a continuous link between green buildings (green roofs, living walls) to functional landscapes.  Connectivity in that continuum to allow energy, nutrients, water, and living things move through urban and rural landscapes.  And conservation, giving the means to allow living things to survive and, critically, EVOLVE into the future.  Blue-green infrastructure is more than “being green” though – for example in the Cevennes Biosphere Reserve in Southern France, the traditional techniques of dry stone wall and terraces for agriculture are being revived, providing new employment opportunities and aesthetic landscape redevelopment, as well as fulfilling all aspects of green infrastructure.

Part of developing and managing blue-green infrastructure is the technique of Ecological engineering – defined as the design of ecosystems for the mutual benefit of people and nature. ecological engineering is intertwined with ecological restoration.  An important question is whether either ecological engineering or ecological restoration will be the right approaches as we enter the Anthropocene.

Bill Mitsch, writing in 2014, notes that “Ecosystem restoration, as currently practiced is done by practitioners with little experience in design and by engineers who do not appreciate the capabilities of ecosystems to self-design”.   He carries on – “The approach of many restorations is restoration by committee – that results in projects that are less successful than anticipated or are over-designed by engineers with unsustainable technology.  For ecological restoration to become more accepted and predictable, the fields of ecological engineering and ecosystem restoration need to be better integrated and more transdisciplinary in universities.’” And finally, “Ecosystem restoration was described by noted British restoration ecologist Tony Bradshaw as ‘ecological engineering of the best kind,’”. This makes a great deal of sense – the best kind of ecosystems we can create or restore are the ones that were there before – or are they?

In fact, restoration ecology, as currently practiced and taught, needs to provide greater allowance for emerging (novel) ecosystems, and not always focus on putting things back to the way they were. This means, simply, that design and problem-solving of mega-ecological problems are needed in the fields of ecological engineering and ecosystem ecology, to develop and maintain blue-green infrastructure. Mitsch (again) has this great quote: “Engineers and scientists alike need to recognize the importance of Mother Nature (self-design) and Father Time (time as a component in ecosystem development) in designing functional ecosystems” – what we might call the Dr Who effect.

A practical example is the Kristianstads Vattenrike Biosphere Reserve in Sweden. Here, blue – green infrastructure is used as a means for adaptive co-management of complex landscapes. This adaptive co-management is:

  • Tailored to local conditions;
  • Flexible and adaptive to ecological changes – management interventions are designed as experiments; and
  • Builds on collaboration between actors on several levels – local stewards, NGOs, governmental institutions, etc.

In Australia, Landcare is a great example of building and caring for blue-green infrastructure.  Like the Swedish example, Landcare Uses Government convening power teamed with Community efforts to implement and maintain blue-green infrastructure.

So, finally, while, blue-green infrastructure has great benefits for our life on earth, we cannot now do away with grey-black either.  We need a blending of both to yield the most effective results – but too much reliance on black-grey infrastructure is not a good “road” to the future.



Mitsch, W.J. 2014 When will ecologists learn engineering and engineers learn ecology? Ecological Engineering 65 9–14

Purdy, J.  2015.  After Nature: A Politics for the Anthropocene.  Harvard University Press. 336pp.


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