REVIEW

Review of "Ecological Engineering - bridging between ecology and civil engineering" by Dr. Ing. Hein van Bohemen

Some preliminary thoughts ...

However, even this rather strict definition can accomodate a wide range of potentially conflicting disciplines. It does not explicitly exclude, e.g., the use of genetically engineered microorganisms or transgenic crops, which many practitioners of Ecological Engineering would exclude for ethical reasons. In the very heart of many, Ecological Engineering is "engineering with an attitude" as David del Porto termed it. But which attitude? If a Living Machine would work better with genetically modified reeds, should we refrain from using them?

To add to the confusion, some proponents of Ecological Engineering concentrate on "designing, monitoring, or constructing ecosystems" (taken from the "Aims and Scope" section of the journal "Ecological Engineering" by Elsevier), whereas others are more interested in the general application of ecological principles. This seemingly small difference has large implications. In the second case, Ecological Engineering principles can be used for all kinds of human activities, such as traffic planning, construction of buildings, financial markets, or even - why not? - computer science.

These two areas of conflict in the back of my mind, I was very curious to read "Ecological Engineering - bridging between ecology and civil engineering". The main author, Hein van Bohemen, is a founding member of IEES. For many years he was the head of the Environmental Research Department of the Road and Hydraulic Engineering Institute of the Ministry of Transport, Public Works and Water Management in the Netherlands.

Hein van Bohemen is also a teacher at the Technical University of Delft, the Netherlands. The book is mainly written as text book for his students. Nevertheless, a book on Ecological Engineering written on this background can be expected to add an interesting perspective to the whole field and may be interesting to a much larger audience.

The core: roads, their effects on the landscape and how to mitigate them

In the Netherlands with one of the world's densest road networks, there are about 113'000 km of roads (about three times around the globe) or 1.63 km of roads per km² (p.199). It is evident that these roads, the traffic on them causing noise, exhaust fumes and other types of pollution are a main factor in landscape ecology. The flattened bodies of frogs, toads, birds or hedgehogs on the roads make clear what habitat fragmentation means in concrete to animals who live along them. If densely populated areas of the world are to remain a habitat for these animals, you need to deal with roads and how their effects can be mitigated.

The strongest part of the book is, in my view, where Hein van Bohemen deals with roads (chapters 9-12). Let us therefore have a closer look at these 4 chapters and ask what Ecological Engineering can contribute to a better design of roads (see table 1 for a complete table of contents of the book).

In chapter 9, the author introduces the theoretical concepts of landscape ecology, e.g., the habitat patch-corridor-matrix model (Fig. 1), the importance of boundaries, the concept of connectivity, ecological networks, ecology of scale and so on. Chapter 10 then zooms on methods to describe, analyze, understand and model ecosystems: systems thinking and systems theory.

In an engineering context, these concepts are important to be taught, even though they are quite familiar to people trained in ecology. The reason: a continuing lack of communication between ecologists and engineers. It dates back to the 1920's when nature conservationists first started worrying about the negative effects of roads and railroads on fauna and flora. But, as the author states (p.204) "it is very probable that (their) suggestions never reached the road engineers who made the actual designs and built the roads". In some instances this will still be the case today.

Chapter 11 then takes a close and detailed look at vegetation and fauna of roadside verges. Here the author goes into great detail. Some of our readers may think, a roadside verge is just a meadow or a lawn alongside the road. In fact, back in the 1960s, management of roadsides was nothing else than lawn maintenance. However, since the 1970s, ecological road verge management has become more and more state-of-the-art in the Netherlands. A closer look was taken at the specific plant societies found along roads and management practices were adapted accordingly, leading to a higher diversity and ecological value of the roadside verges. The interesting role of roads as migration corridors for plants was discovered. And: plant species that usually grow on small salt dunes in salt marshes can now be found along Dutch roads. A clear side effect of winter maintenance with salts.

Looking at fauna, road killings are the most obvious effect of roads on animals. Yet, the connections between different factors are sometimes hard to understand. An example: For the barn owl, traffic on the A6 motorway is attributed to more than 50% of the annual mortality in the Dutch province of Flevoland (p. 211). Why would owls be attracted to roads? Ecological roadside management provides rodents with more food than the monotonous arable land and grassland in the surroundings. The rodents in turn are prey for the owls. The barn owls also like to use kilometer signposts as lookout posts - a high risk place for a bird. In this example, a different management practice of the roadside verge and a different design of the kilometer posts could help to improve the situation for the barn owl.

In other cases, however, birds have even taken advantage of roads. For example, areas within clover leaves of motorways have surprisingly attracted mixed colonies of gulls and terns. The lack of ground predators and humans during the breeding season seem to be the reason for establishing successful colonies even in spite of the roaring traffic all around. Nature is always good for a surprise!

Chapter 12 focusses on fragmentation and defragmentation, and on concrete measures that can be taken. There is a rich choice of different examples in this chapter, ranging from fauna tunnels (so called "culverts") to ecoducts (= fauna passages, fauna bridges) to special measures for bats. Bats, for example, tend to fly along vegetated strips, so a conscious planting of "hop-over" trees can provide save overpasses for them (see Fig. 2). An analysis of the Dutch defragmentation policy is also documented that lead to the selection of 10 priority areas where bottlenecks for the fauna are indentified and will be addressed in a multi year program.

Apart from these 4 selected chapters, the author has taken a great deal of effort to embed the whole conceptual background of Ecological Engineering and make it accessible to students of engineering.

What I like best about the book is the great variety of examples and case studies that can serve as a reference for further study and research. Together with the theoretical background of the "larger picture" (e.g., chapter 4: ecological sustainability, chapter 6: concept of nature, chapter 7: overview of goods and services) the book provides a valuable resource for readers and learners. This and the uniqueness of its scope make the book a recommended reading for a wide range of disciplines. My favourite chapter is 5.6 where the range of potential applications of Ecological Engineering is demonstrated with the help of 10 case studies.

Some suggestions for further improvement

A drawback of the book is its heavy focus on the Netherlands, which also becomes evident in quite a few figures that have not been translated to English. It is of course a basic dilemma of any such book that the true value of Ecological Engineering can only be shown with the help of cases and examples. An author will usually have the best knowledge about cases from his/her own work experience. So, a detailed presentation of cases from one country will lead to neglecting cases from other parts of the world. It remains a task of the readers to look for examples in their own context.

A second drawback: The case studies, however, although consisting of interesting examples, leave an impression of being rather unrelated to each other (many of them are written by guest authors). It would have been very helpful for me as reader, if they had at least all followed the same structure. I am also missing an explanation why all these cases can be called Ecological Engineering.

Last but not least, an index would very much of help to find ones way through the wealth of information Hein van Bohemen has collected.

All in all, I am glad about this book and hope that it will help to bridge the gap between ecologists and engineers, just as the author intended it.