Evolutionary Conservation of Species’ Roles in Food Webs

Stouffer, D.B., Sales-Prado, M., Sirer, M.I. & Bascompte, J.

For several years, conservation efforts around the world have been focused on single species (keystone, flagship and umbrella species). This approach has been criticized mainly for not considering ecological processes, and therefore being ineffective for preserving ecosystems (Simberloff, 1998). Nowadays, conservation programs are being planned based on a holistic approach, taking into consideration the functioning ecosystems and their associated ecosystem processes (Wilson et al., 2009). It is broadly known that the structure of a community and its capacity to remain functional are connected in a complex manner. Nevertheless, the degree of influence of a species’ identity on the persistence of the community it belongs to, as well as the variation degree of a species’ role as function of its community, is still uncertain. In order to fill that gap in our knowledge, this week’s discussion paper proposes a mathematical model based on “network motifs” that aims to determine the role played by a species and its importance in dynamics of a community. This model was tested using data from 32 empirical food webs from different environments, concluding that the species´ roles and their dynamic importance are inherent and intrinsic features developed as part of the evolution of taxa. Thus, some taxonomic groups tend to play the same role in different communities.

During our discussion, the group concluded that although the approach seemed very useful, the conclusions from the modelling were not new and that the authors could have done more to show how the model could be applied to the conservation of species and communities. Furthermore, some concepts like “benefits of the species” and community persistence were not properly explained in the main paper, leading to some confusion.

Question:

Besides identifying species’ roles in communities, how could this model be applicable and helpful in establishing conservation priorities?

References cited:

Simberlof, D. (1998). Flagships, umbrellas, and keystones: is single-species management passé in the landscape era?. Biological Conservation 83(3) 247-257.

Wilson, K. A., Carwardine, J. and Possingham, H. P. (2009), Setting Conservation Priorities. Annals of the New York Academy of Sciences, 1162: 237–264

Novel urban ecosystems, biodiversity, and conservation

Urban areas cover only approximately 3% of the total area of the earth’s land surface but urban growth is regarded as a major threat to biodiversity (Kowarik, 2011). 50% of the worlds population lives in urban areas and is increasing at an average annual rate of 1.9% (UN,2011). The importance of biodiversity in cities is seen by many to be not only a conservation issue but also a human health issue. Urban Ecology has a long history mainly in Europe. The succession of vegetation in bombed ruins of the Second World War was studied in many cities and in the 1970s ecological studies in cities started with investigations on energy flow and nutrient recycling. Urban ecology is now seen as a way to develop more sustainable cities and a mechanism to investigate how living organisms relate to their environment in cities (Sukopp, 2002).

This week’s discussion questioned the ecological role of increasing native biodiversity in urban areas. Are there benefits in trying to understand or enhance the ecological processes that may be occurring though increased native biodiversity? Kowarik (2011) states that conserving and enhancing urban biodiversity benefits human wellbeing and public health. Biodiversity also provides opportunities for people to interact with nature more often and therefore fosters a wider interest in nature conservation issues (Goddard et al. 2010). Has the social science behind these observations been studied and quantified? There is definitely a feel good factor in being part of restoring natural diversity to a city as seen by the number of groups involved in restoration in Christchurch and surrounding areas. But does this foster a greater interest in protecting our truly wild areas? A concern raised was that money could be diverted from conservation issues to fund biodiversity enhancement in urban areas giving little benefit to ecosystem functions.
What kinds of ecosystem functions can we create or restore in cities?

Cities as a whole are human-generated (Hobbs et al. 2006) novel systems, where species are thrown together in communities of compositions not found in nature. Urban ecology has shown cities to have both negative and positive impacts on biodiversity. Much of the plant diversity within a city is of an exotic nature causing cities to be hotbeds for exotic garden escapees, which can become pests in natural landscapes. On the other side of the coin can urban areas be seed sources and/or refuges for rare or endangered native species?

What is the scientific (and other) value of doing Urban Ecology? To answer this question I feel more research is needed on urban biodiversity and its related ecological and social implications.

References cited
Goddard, M. A., A. J. Dougill, and T. G. Benton. 2010. Scaling up from gardens: biodiversity conservation in urban environments. Trends in Ecology and Evolution 25:90-98.

Hobbs, R., S. Arico, J. Aronson, J. S. Baron, P. Bridgewater, V. A. Cramer, P. R. Epstein, J. J. Ewel, C. A. Klink, A. E. Lugo, D. Norton, D. Ojima, D. M. Richardson, E. W. Sanderson, F. Valladares, M. Vila, R. Zamora, and M. Zobel. 2006. Novel ecosystems: theoretical and management aspects of the new ecological world order. Global Ecology and Biogeography 15:1-7.

Kowarik, I. 2011. Noval urban ecosystems, biodiversity, and conservation. Environmental Pollution 159:1974-1983.

UN, 2011. Urban Population and Development 2011. UN, New York United Nations Department of Economic and Social Affairs. Population Division.

Biodiversity and ecosystem function

The ‘biodiversity and ecosystem function (BDEF) debate’ that has raged in ecology for several decades specifically addresses the question: Given the current unprecedented rate of extinction on Earth, to what extent does the loss of species affect how stable ecosystems are and what functions and services they provide? For instance, what is the effect of decline in plant species richness from a grassland ecosystem on properties such as nutrient cycling, decomposition rates, water capture and carbon sequestration? Numerous studies have shown that biodiversity influences ecosystem processes (and vice versa). In recent reviews, such as Naeem et al. (2012), which we discussed this week, it appears ecologists are trying to synthesise this large volume of work (showing that biodiversity does indeed have an effect on ecosystem function) and move the field on to the next stage of maturity – what have we learned over the last 20 years, how can we use this information and what should we be researching now? We felt that the Naeem et al. paper has some useful points in it, such as a box explaining seven ‘dimensions’ of biodiversity that provide six different ways of examining the effects of diversity on ecosystem function besides (the probably overused measure) species richness. The authors offer some well-stated challenges for future researchers including demonstrating effects in larger-scale, natural systems, accounting for these multiple forms of diversity as well as multiple ecosystem functions in their projects, using small amounts of information on species’ traits to predict trait states across greater numbers of species within ecosystems, and to start making the most of advanced technology such as pyrosequencing and newer statistical methods. The authors also remark on the importance of considering cultural values of biodiversity as another ecosystem service because although it is a non-utilitarian aspect of conservation, it is also important in terms of maintaining biodiversity.

Our discussion of this paper started us thinking about how useful the BDEF relationship is to ecology, conservation, and restoration ecology. We concluded first that the demonstration that biodiversity loss can impact ecosystem function justified what many of us do (try to understand spatio-temporal patterns in biodiversity in its various forms). Second, we discussed the notion that given that much of conservation applies to rare species conservation and the removal of rare species (e.g., the flightless New Zealand takahē (Porphyrio hochstetteri), decline in tussock grasslands of the South Island), doesn’t appear to affect the functioning of their native ecosystem, is it something that conservationists need to know or worry about? We concluded that the BDEF research was most relevant to restoration ecology where practitioners should want to know about the ecosystem-level effects of their efforts. We talked about integrating different measures of diversity and multiple ecosystem functions into our monitoring of restoration success.

We then moved on to a discussion of differences between ecosystem functions and ecosystem services and how these things might be measured in a restoration context. We talked about the effect of scale on evaluating restoration success, what restoration success was in general and what questions we needed answers to in order to make ‘recommendations’ to land managers who wanted advice on restoring a given area of land. We also debated the constraints on our ability to feed everyone on Earth now and into the future.

Questions:

·       We started to talk about how we would measure things in a real system, such as a restoration experiment, but it would be worthwhile to think more about this. How can ecosystem functions be measured? How can ecosystem services be measured?

·       Several other recent review papers were suggested to be relevant to our debate including Cardinale et al. (2012), Ehrlich et al (2012), and Hooper et al. (2012). How are these differ from the Naeem et al. paper?

References cited

Cardinale, et al. 2012. Biodiversity loss and its impact on humanity. Nature 486: 59-67.

Ehrlich et al. 2012. Securing natural capital and expanding equity to rescale civilization. Nature 486: 68-73.

Hooper et al. 2012. A global synthesis reveals biodiversity loss as a major driver of ecosystem change. Nature 486: 105-109.

Naeem et al. 2012. The functions of biological diversity in an age of extinction. Science 336: 1401-1406.