Ecologists aim to develop robust rules to explain how plant and animal communities come to be assembled as they are. These rules should explain,
for example, why some plant communities have many more species than others, or why plant communities often differ markedly in structure under
seemingly similar conditions. Ecologists should also address ecosystem management, so that research findings can be put to practical use. One
approach to addressing these questions has been to examine the structure, composition and management of ecosystems that experience similar
conditions in different parts of the world. Comparative studies of Mediterranean-type ecosystems (MTEs) provide an example of such an approach,
and have been conducted for almost 40 years.|
Mediterranean-type ecosystems share a climate characterised by cool, wet winters and warm, dry summers, and these ecosystems support vegetation
that is typical of particular regions – fynbos in the Cape; chaparral and coniferous forests in California; kwongan, heaths and dry
sclerophyll forests in southern Australia; maquis and garrigue in the Mediterranean basin; and matorral in Chile. These ecosystems cover just 5%
of the earth’s land surface, yet they contain 20% of the world’s plant species, many of which are not found anywhere else. A pervasive
feature of these areas is the frequent occurrence of intense fires in the dry summer season. Historically, biogeographers and ecologists have
attempted to explain the structure and composition of vegetation in terms of climate and geology alone. One of the more recent contributions
arising from the study of MTEs is an understanding of the critical role that fire plays in shaping vegetation. A central theme of the book is
that plant communities cannot be understood without considering the climate–fire–geology filter that controls the assembly of these
systems. Another uniting theme within fire-adapted and fire-dependent MTEs is how ecosystem managers can ensure the survival of the remarkable
biodiversity that coexists cheek by jowl with dense human settlements.
The tale unfolds in this book in three parts. The first is a broad introduction to MTEs and fire; fuels, fires and fire regimes; fire-related
traits in plants; and how plants respond to fire regimes. The second addresses each of the five MTEs separately, covering aspects of the
vegetation, fire environment and fire ecology. The third part compares and synthesises the evolution of fire adaptive traits, how fire regimes
originated in MTEs and came to shape the modern vegetation, and how these systems are managed.
The vegetation of MTEs is remarkably variable, ranging from sparse shrublands to forests. Fires in these ecosystems include crown fires that
kill most of the vegetation, and surface fires that burn in the understory of forests; these fire types differ significantly in frequency and
intensity. Understanding these regimes is fundamental to interpreting the many and varied responses of component plant species. The vegetation
is often a complex mix of plants that resprout after fire, plants that are killed by fire and have to ensure their seed survival and germination,
and plants that are able in other ways to attune their reproduction and dispersal to fire-prone environments.
It is not only the similarities between MTEs that are of interest – the differences are equally fascinating. Fire is a pervasive feature of
each of the MTEs, but in each it plays out in very different ways. In Chile, fires have not been a feature of the landscape since the Miocene,
when the rising Andes prevented convective thunderstorms from progressing eastwards, robbing the vegetation of a ready source of ignition. As a
result, there are fewer fire-adaptive traits in matorral plants, although some plants that retain these traits linger in the landscape as relicts
of a past that featured frequent fire. Following European settlement in 1880, fires once again became common in the Chilean matorral, and are a
regular feature of the area. In the Mediterranean Basin, an increase in fire has been driven by emigration rather than immigration. Centuries of
human settlement created a cultivated landscape in which fires were relatively rare. Socio-economic changes in the 1970s were accompanied by
rural depopulation, abandonment of farmlands and a reduction in grazing pressure, leading to a build-up of fuels and an increase in the number,
size and severity of fires. California is different in that it has varied fire regimes that include intense crown fires in shrublands and
relatively low-intensity fires in conifer forests, sending the vegetation on very different trajectories of evolution and responses. Relatively
low-nutrient environments in the Cape and Australia have driven the evolution of vegetation that is much richer in species than that of the
northern hemisphere MTEs.
South African readers will have a particular interest in the account of fynbos fire ecology, and this book provides the first comprehensive
synthesis of this topic since the publication of The ecology of fynbos1 20 years ago. Surprisingly, this earlier volume had no
chapter dedicated to fire, although fire was addressed in a chapter on management. The latest synthesis therefore contains a greater depth of
coverage than has existed before, and there is also much that is new. Recent research has highlighted the dynamic and competitive interactions
between overstory and understory plants that significantly influence the nature of post-fire communities. This research is in contrast to earlier
views that explained post-fire assemblages in terms of fire survival attributes only. More recent research has also revealed important differences
in plant responses to fires in different seasons between the eastern and western parts of the fynbos. Now, fire regimes, and how they are
influenced by management practices, are also far better understood.
The comparative study of MTEs in relation to fire allows for the identification of characteristics of divergence or convergence
– ‘emergent properties’ – that would not have been evident from the study of any one of the regions in isolation. Plants
have to cope with an environment in which the vegetation forms a continuous fuel bed that supports spreading fires over large areas. Traits have
evolved to include a mixture of re-sprouting and of fire-dependent reproduction, where closed canopies prevent recruitment in mature stands and
where seedlings must exploit the resources released by fire to survive and grow. Both traits have persisted because fire regimes are not predictable
enough for either to gain dominance. Studies of the origins of Mediterranean-type vegetation have until recently focused largely on the role of
climate and soil fertility as determining factors, and fire has received scant attention. However, the Mediterranean climate’s seasonally
high temperatures and dry conditions have combined to expand fire’s footprint on the landscape, which has had profound effects on the
vegetation. But the prevailing order is changing rapidly in the face of invasions by alien plants, which often are moved from one MTE to another.
These alien plants are frequently spread by fire, and are changing fuel conditions and fire regimes, with devastating consequences for the
diversity and functioning of some systems.
Another aspect within the book that will be of interest to South African readers is the almost trivial nature of our ‘fire problem’.
While wildfires in the Mediterranean Basin, California and southern Australia can – and have – destroyed thousands of dwellings in a
bad fire year, the extent of damage in South Africa is typically two to three orders of magnitude smaller. This difference is partly as a result
of less severe fire conditions, and partly because of ’hard’ edges between urban areas and the veld, a legacy of good planning in the
past. Nonetheless, the problem in South Africa is set to grow as populations grow, and the need to reconcile competing demands for safety and
ecological health in fire-adapted ecosystems will tax managers of the future, despite the relatively minor magnitude of the current problem.
Overall, this book provides a remarkably comprehensive treatment of an important topic. Syntheses of this nature cannot be found in journal
papers or even in special journal issues dedicated to one or another topic. While most ecological books are either written by one or two experts,
or are edited volumes with multiple authors, this book is unusual in that it has five authors who have taken joint responsibility for all of the
material presented. Each author is a leading world expert in fire ecology, and each calls one or the other of the major MTEs home. Collectively,
these authors have more than two centuries of experience, and the depth and scope of their insight is reflected in this book. Almost one fifth
of the book (100 pages) contains the references – testimony to the breadth of coverage and a valuable resource in itself. As such, this
book should prove indispensible to graduate students, researchers and managers of fire-prone MTEs, and I would recommend it unreservedly.
1. Cowling RM. The ecology of fynbos: Nutrients, fire and diversity. Cape Town: Oxford University Press; 1992.
Mass flowering in the geophyte Watsonia borbonica in the spring following a summer fire in the Jonkershoek valley near Stellenbosch. The
dead Protea shrub was
killed in the fire and would have released seeds to germinate in the post-fire environment. Mass flowering and fire-stimulated mortality and
seed release are two
common adaptations to fire in several Mediterranean-type ecosystems (photo: Brian van Wilgen).