Multiple benfits from tree plantings for carbon farming

Tree planting for carbon can potentially also provide a range of other benefits beyond just carbon. For the farmer this includes pest control and pollination services to crops, protection of livestock, and a reduction in soil erosion and salinity. For the wider community this could include increased water quality and more habitat for species such as birds. Dr. Brenda Lin and collaborators (including myself) have just published an article in BioScience exploring the range of benefits and potential dis-benefits that may occur as a results of tree planting activities. We found that there are a range of options for tree planting in agricultural landscapes for carbon, but they don’t all have the equivalent ecological benefits. If we want these additional benefits we do need to carefully think about the implementation of these schemes at a range of spatial scales.

BioScience Press Release with link to a version of article published ahead of print.

Further information about this article in the media can be found here and here.

The humble tree can provide a lot beyond just carbon storage (photo credit: M. Neave, CSIRO)

The humble tree can provide a lot beyond just carbon storage (photo credit: M. Neave, CSIRO)


Edges in Agricultural Landscapes: Species Interactions and Movement of Natural Enemies

New paper published in PLOS ONE

This is a paper in which Warren Muller and I illustrate how insects moving through agricultural landscapes perceive different edges or eco-tones. We combine this movement data with information on species interactions (herbivores-parasitoids) to discuss the implications for pest control services.

Let me know what you think of the paper and if you are currently doing any work around insect movement in agricultural landscapes.

Macfadyen S, Muller W (2013) Edges in Agricultural Landscapes: Species Interactions and Movement of Natural Enemies. PLoS ONE 8(3): e59659. doi:10.1371/journal.pone.0059659


Modelling the Geographical Range of a Species with Variable Life-History

New pest modelling paper published in PLoS ONE.

Let me know what you think by adding comments to the PLoS ONE comments page of the article:

Macfadyen S, Kriticos DJ (2012) Modelling the Geographical Range of a Species with Variable Life-History. PLoS ONE 7(7): e40313. doi:10.1371/journal.pone.0040313

In this paper Darren and I show how a climatic niche model can be used to describe the potential geographic distribution of a pest species with variable life-history, and illustrate how to estimate biogeographic pest threats that vary across space. The models were used to explore factors that affect pest risk (irrigation and presences of host plant).

A combination of current distribution records and published experimental data were used to construct separate models for the asexual and sexual lineages of Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) (bird cherry–oat aphid).  Rhopalosiphum padi is a pest of cereals in many countries around the world. Farmers rely heavily on the use of insecticides to control this pest, particularly in winter wheat and barley crops across Europe, as it is a vector of crop diseases. The two models were combined with knowledge of host plant presence to classify the global pest risk posed by R. padi.

Map of the world, showing risk categories for Rhopalosiphum padi invasion.


Two scenarios are shown that represent; (a), natural rainfall conditions; and (b), an irrigation scenario. Results are based on the output from sexual and asexual CLIMEX models and the presence or absence of the primary woody host plant. Invasion risk categories are based on the International Standard for Phytosanitary Measures (ISPM) (FAO 2006). ‘Endangered’ indicates areas that are at risk of R. padi populations establishing and persisting year-round, ‘Transient’ indicates areas that are at risk of seasonal reinvasion but conditions are not suitable for persistence year-round, and ‘Potentially endangered’ indicates areas at risk of persistent populations year-round if a suitable Prunus host plant were introduced. doi:10.1371/journal.pone.0040313.g004

The enemy within: Wolbachia increases the susceptibility of armyworm to viral disease

Interesting paper: Robert I. Graham, David Grzywacz, Wilfred L. Mushobozi and Kenneth Wilson Wolbachia in a major African crop pest increases susceptibility to viral disease rather than protects Ecology Letters 15
DOI: 10.1111/j.1461-0248.2012.01820.x

I just read an exciting paper that shows that field populations of the African armyworm (Spodoptera exempta) that are infected with an endosymbiont bacteria Wolbachia are more susceptible to mortality due to a nucleopolydrovirus (SpexNPV). Wolbachia are common intra-cellular bacteria found in many insect species, and can protect their hosts from viruses. Researchers are trying to use Wolbachia to reduce the ability of mosquito’s to transmit dengue viruses to people. What Graham et al. have shown is that in the future it may be possible to use the wide-spread infection of armywom by Wolbachia to enhance our efforts to kill this pest using a biopesticide.

New paper out: Parasitoid diversity reduces the variability in pest control services

My latest paper from the organic farms study in the UK has just come out. You can download from here or contact me for a copy.

Macfadyen, S., Craze, P., Polaszek, A., van Achterberg, K. & Memmott, J. (2011) Parasitoid diversity reduces the variability in pest control services across time on farms. Proceedings of the Royal Society B, 278: 3387-3394.


Recent declines in biodiversity have increased interest in the link between biodiversity and the provision and sustainability of ecosystem services across space and time. We mapped the complex network of interactions between herbivores and parasitoids to examine the relationship between parasitoid species richness, functional group diversity and the provision of natural pest control services. Quantitative food webs were constructed for 10 organic and 10 conventional farms. Parasitoid species richness varied from 26 to 58 species and we found a significant positive relationship between parasitoid species richness and temporal stability in parasitism rates. Higher species richness was associated with lower variation in parasitism rate. A functional group analysis showed significantly greater parasitoid species complementarity on organic farms, with on average more species in each functional group. We simulated parasitoid removal to predict whether organic farms experienced greater robustness of parasitism in the face of local extinctions. This analysis showed no consistent differences between the organic and conventional farm pairs in terms of loss of pest control service. Finally, it was found that the different habitats that make up each farm do not contribute equally to parasitoid species diversity, and that hedgerows produced more parasitoid species, significantly more so on organic farms.

Interesting paper – network analysis….a guide for community ecologists

I found this great ‘invited view’ paper in Basic and Applied Ecology that explains the problems and pitfalls of using a range of network metrics to describe network topology. Very useful for any ecologist involved with, or wishing to embark on, network analysis.

The full reference is:

Nico Blüthgen (2010) Why network analysis is often disconnected from community ecology: A critique and an ecologist’s guide. Basic and Applied Ecology 11:185-195.

Link to Journal website

Interesting paper

Googling Food Webs: Can an Eigenvector Measure Species’ Importance for Coextinctions?

Predicting the consequences of species’ extinction is a crucial problem in ecology. Species are not isolated, but connected to each others in tangled networks of relationships known as food webs. In this work we want to determine which species are critical as they support many other species. The fact that species are not independent, however, makes the problem difficult to solve. Moreover, the number of possible “importance’” rankings for species is too high to allow a solution by enumeration. Here we take a “reverse engineering” approach: we study how we can make biodiversity collapse in the most efficient way in order to investigate which species cause the most damage if removed. We show that adapting the algorithm Google uses for ranking web pages always solves this seemingly intractable problem, finding the most efficient route to collapse. The algorithm works in this sense better than all the others previously proposed and lays the foundation for a complete analysis of extinction risk in ecosystems.

Stefano Allesina and Mercedes Pascual
PLoS Computational Biology Vol 5, Issue 9, e1000494

The authors have developed an algorithm based on the one Google uses to rank web-pages to order species in a network in terms of their importance for coextinctions. Their algorithm outperformed other measures of robustness to species loss. When examining 12 published food webs their results suggest that the position of a species in the food web is an important determinate of impact on extinction cascades.

Interesting paper

Compartments in a marine food web associated with phylogeny, body mass, and habitat structure
Ecology Letters (2009) 12(8), 779-788
Enrico L. Rezende, Eva M. Albert, Miguel A. Fortuna, Jordi Bascompte

doi: 10.1111/j.1461-0248.2009.01327.x

Rezende et al. examined network structure in a marine food web (containing 3313 interactions between 249 species/trophic groups!) and unequivocally showed the presence of compartments (or subunits) in this network. These are link-dense regions of the network where species interact more closely with other species within the module than between modules. Modules may may be important for the propagation of disturbance impacts throughout a network.  More importantly Rezende et al. identified some potential mechanisms behind this interesting network structure (body size, phylogeny and spatial structure).  Shark species played an important role in this network.