{"id":1010,"date":"2013-12-11T21:29:29","date_gmt":"2013-12-11T10:29:29","guid":{"rendered":"http:\/\/ecogeog.com\/blog\/?p=1010"},"modified":"2013-12-11T21:29:29","modified_gmt":"2013-12-11T10:29:29","slug":"multiple-stable-states-in-natural-ecosystems","status":"publish","type":"post","link":"http:\/\/ecogeog.com\/blog\/?p=1010","title":{"rendered":"Multiple Stable States in Natural Ecosystems"},"content":{"rendered":"

\"petraitis\"<\/a>Rating:<\/strong> \"☆\"\"☆\"\"☆\"\"☆\"\"☆\"<\/p>\n

Peter Petraitis. 2013. Multiple Stable States in Natural Ecosystems. Oxford University Press. ISBN 978 0 19 956934 2<\/strong><\/a><\/p>\n

One of the more pressing issues we face when considering wicked problems like global climate change is the likely fate of ecosystems. Common amongst the general comments are the ideas of\u00a0 “tipping points<\/a>”\u00a0 – a set of conditions “beyond” which there will be a change of ecosystem state that cannot be reversed. This might seem “reasonable” but it depends on your values! For those who support the notion of climate change, this could taken as a total loss of all ecosystem services; almost the contrary for those not in agreement. One of the more difficult points is to find evidence. We have no lack of models but showing in as an actual ecosystem change is another matter.<\/p>\n

An opening sentence in this book explains the point more clearly:<\/p>\n

“One of the most interesting and vexing problems in ecology is how natural ecosystems can appear so persistent and yet seem so susceptible to catastrophic change…Often the shifts are not only quite dramatic and occur without warning but also are very difficult to reverse”<\/em><\/span> (p1)<\/p><\/blockquote>\n

Here is the issue – an idea that the same area can maintain totally different ecosystems at different times and yet equally stable results. To explain this, the concept of multiple\u00a0 stable states was introduced. Creating a concept is one thing; finding evidence to support it is another. We start with two examples – the shift from wet to dry sclerophyll forest in S.Australia and the loss of Passenger Pigeons<\/a> in the US. In the former case, woodland was replaced by more open. drier conditions; in the latter the change was between numerous and no pigeons. In both cases the area continued but with different species (of numbers of species).\u00a0 Chapter two explores the ideas of models in greater detail. Starting with some simple models, we are introduced to the theoretical ideas of stable states. Two examples\u00a0 will suffice. The Allee effect states that populations will grow more the larger the number. The corollary notes that at low population densities, populations will disappear irrespective of\u00a0 resources e.g. species extinctions at low levels. Another case uses the ridge-and-ball metaphor whereby a ball rocking on a corrugated surface will suddenly have enough momentum to push over the peak to the next valley. Thus theoretical study supports the idea.<\/p>\n

Chapter three examines how we might detect such states – what types of experiments might we set up? The argument is made that is this discrete field of study, many of the experiments do not lend themselves to replication and so a portion of the text focusses on the parameters needed to design a test. Next, we are taken one stage further to examine which experiments actually meet the criteria discussed. The reader quickly gains two key pieces of information: that there are very few tests anywhere near the idea of multiple states and of theses few, even fewer actually fit the criteria stated. At first glance, this seems surprising because the main criteria (the Peterson criteria) appear, on the surface, to be very reasonable: same site, different communities and self-replacement. This is apparently very difficult and even the “best” experiments are found to have flaws. The conclusion here is that if we are to prove beyond reasonable doubt that multiple states exist, we need to be far clearer on the experimental design than heretofore.<\/p>\n

For the next two chapters, the book takes a different turn. Multiple states are often associated with catastrophe theory but this is not an area that many ecologists have used. Whereas this is changing, there is still a lot to do. We need to start with an brief introduction to catastrophe theory and how it fits into the idea of multiple states. The next move is to show what sorts of multiple states a catastrophe theory could explain\/support.<\/p>\n

Not all the work is carried out with catastrophe in mind. Many models of stable states are theoretical – they seek to provide a pattern based on observations but without the gathering of data. Functional models on the other hand tend to be more mathematical and might even involve simulation exercises. Whatever the models, there are going to be limitations. Having examined catastrophe theory, the reader is asked to examine four more misconceptions surrounding multiple states. These misconceptions involve thresholds, multiple states, model variables and parameters and the universality of the multiple state. Each one, in turn, is subjected to analysis and are largely rejected. If the work gets through this examination, then the next stage is to question the evidence to ensure that it meets the criteria for a valid experiment. Each area, it seems has issues. A brief concluding chapter suggests ways forward.<\/p>\n

This is a fascinating study of one of the most crucial but seemingly less studied aspects of ecology. That multiple states should exist seems reasonable on the surface because don’t we see woodland removed to make way for farmland that is stable (although we don’t often argue the time factor here!). However, the closer one gets to understanding this potential phenomenon, the more issues we seem to find. There appears to be very few (no?) cases that meet all the various criteria mentioned here. What we have is a book that lays bare the issues surrounding a\u00a0 concept. As such, although it is clearly aimed at the advanced reader, it provides us with an interesting insight into the arcane world of modelling and experimentation.\u00a0 This makes it a book suitable on many levels – theory, fieldwork design, modelling, analysis etc. Its careful, almost clinical approach to dissecting the topic should appeal to many who wish to see rigour continue in the subject.<\/p>\n","protected":false},"excerpt":{"rendered":"

Rating: Peter Petraitis. 2013. Multiple Stable States in Natural Ecosystems. Oxford University Press. ISBN 978 0 19 956934 2 One of the more pressing issues we face when considering wicked problems like global climate change is the likely fate of ecosystems. Common amongst the general comments are the ideas of\u00a0 “tipping points”\u00a0 – a set of conditions “beyond” which there will be a change of ecosystem state that cannot be reversed. This might seem “reasonable” but it depends on your […]<\/p>\n","protected":false},"author":1,"featured_media":916,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[45,270,181],"class_list":["post-1010","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-review","tag-ecology","tag-ecosystem-states","tag-theory"],"_links":{"self":[{"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1010"}],"collection":[{"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1010"}],"version-history":[{"count":2,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1010\/revisions"}],"predecessor-version":[{"id":1012,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1010\/revisions\/1012"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=\/wp\/v2\/media\/916"}],"wp:attachment":[{"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1010"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1010"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/ecogeog.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1010"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}