Tag Archives: conservation

Network ecology is dead, long live network ecology!

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Carsten F. Dormann writes a provoking book chapter entitled “The rise, and possible fall, of network ecology” openly criticizing the concept of network ecology. Read it, I enjoyed it.

In fact, despite using network theory in some of my papers, I never liked the term network ecologist, and I never presented myself as such (but I’ve been presented as a network ecologist). For me, being a network ecologist would be like being a GLMM ecologist, or a differential equation ecologist. Networks are tools, not ends.

I believe that things interact with things. While simple systems do not require complex network theory, complex systems can benefit from it, but in agreement with Carsten, only if well applied. Unfortunately, some tools are over-(and miss-)used, such as topological indexes, while others are under-used, such as exploring network dynamics. It is paradoxical that the creator of the bipartite package, which popularized the blind use of multiple topological indexes not necessarily related to processes, is now warning about it.

One of my major concerns about “network ecology” is that many “network” papers are question free. If you don’t have a question, do not use networks. I don’t think answering how index X changes along Y is a valid question as change is the only constant in ecology. I also agree many tools from networks have analogous community ecology metrics, but this is fine with me as it reflects different ways of thinking. So let’s see a few examples of instances where I think network tools can bring exciting complementary veiws:

  • To measure indirect and higher-order interactions. The neighbour of my neighbour can still influence me even if I never meet him/her. How important are indirect interactions in ecology? How do we account for their effects on fitness? Many open questions where a network perspective can help.
  • To assess community stability. There is a lot of work using population dynamic models linked through species interaction networks that can help elucidate which interaction structures are compatible with stable communities and why.
  • To describe entire multi-species communities with different interaction types. We can’t even describe how entire communities look like. Networks are good tools for describing patterns, which is the first step to asking questions about processes.
  • To model the flow of “information”. Diffusion networks are under-used as a tool to model how things move through a network. Like pollen grains*

So I agree with Carsten on the fact that “Network ecology” should fall, but i think network analysis applied to ecological problems should prevail!

* we barely scratch the surface on this topic here: Allen-Perkins et al. (2024), Multilayer diffusion networks as a tool to assess the structure and functioning of fine grain sub-specific plant–pollinator networks. Oikos e10168. https://nsojournals.onlinelibrary.wiley.com/doi/abs/10.1111/oik.10168

Why do we need to protect bees?

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This is a very tricky question. Recent media coverage and policy makers are increasingly using the “ecosystem services” argument to justify the conservation of bee populations. Bees are indeed providing us with a precious service, the pollination of 75% of our crops. However, “bees” are a diverse group of more than 20.000 species. David Kleijn had the wonderful idea to check how many of those bee species are responsible of crop pollination and I was more than happy to help him find out. This is the resulting paper. Surprisingly very few species made most of the crop pollination job. Moreover, those species are the ones of least conservation concern, as I already showed here.

What does this means? We should enhance agro-ecosystems to maximize crop pollination by bees. There is no doubt about this and repeated papers had shown that more green infrastructure enhance pollinator densities and thereby pollination. BUT if we want to protect the bee species that really need our help, other measures and incentives are needed beyond ecosystem service delivery. Those threatened species pollinate wild plants, parasite other bees (potentially regulating populations) or are part of larger food webs. Conserving rare bees and other animals should be done without an economical incentive in mind, otherwise, conservationists selling the idea that biodiversity should be conserved because it provide us with services may end up shooting them selfs in the foot by allowing policy makers to protect only the species that are of any immediate use.

Is there a pollination crisis?

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After some months writing this blog, finally I can do some self-promotion and post about our new article just published in PNAS.

Do you think we are experiencing a pollinator crisis? Take note of your answer and keep reading.

In this paper, we show that most Northeastern US bee species persisted along the last 100 year. And those are 100 years that has transformed the landscape dramatically. However, we show that community composition changed markedly. The loser species are some big species, often specialists and with short activity periods. See a quick figure I made trying to capture the essence to outreach people who only have one minute to spare.

BartomeusPNAS

So, what that tell us about a possible pollination crisis? A crisis is something that leads to an unstable and dangerous situation, in this case regarding the fate of pollinators and the service they deliver. Nobody talks about a bird crisis. Some bird species are doing great, some are threatened with extinction, but nobody would dare to generalize about the fate of all bird species as a whole. I think is time we take the same approach with such a diverse group as the pollinators (including bats, birds, butterflies, bees and a long etc…). In this paper we show that some bumblebees (e.g. Bombus impatiens) are doing great, while others are on the brink of extinction (e.g. Bombus affinis). We need to understand better species responses and stop crying wolf for all pollinators. There is a fine line between raising general aware among citizens about the importance of pollinators and their conservation and an overestimated alarmist call. Every time a farmer reads about the pollination crisis while seeing that his field is full of bees buzzing around, we (scientists) are loosing credibility.

Moreover, if is crop pollination and food security what concerns you, it may be that the winner pollinator species, those that thrive in human dominated landscapes, are also the best ecosystem service providers. And if it’s biodiversity (and its overall functioning) what you want to protect, then we should look at which species/habitats needs maximum conservation. We need to move forward and pose the relevant questions, instead of looking for a general declining pattern that hopefully is not really there.

I am expanding too much for my taste, so more on that next week. But to make clear my point: we need to keep studying pollinators (keep funding me!), but next time you cite worldwide pollinator declines, cite me also (i.e. Pots et al 2010, but see Bartomeus et al 2013).

Bartomeus I., Ascher J.S., Gibbs J., Danforth B.N., Wagner D.L., Hedtke S.M. & Winfree R.  Historical changes in northeastern US bee pollinators related to shared ecological traits, Proceedings of the National Academy of Sciences,   DOI:

*Giving the importance of the subject, it was specially important for us to make all historical bee data available @datadryad (dx.doi.org/10.5061/dryad.…) for further analysis and replicability.