Author: AJ Tanentzap

About AJ Tanentzap

University Lecturer leading a research group interested in predicting how ecosystems will respond to future changes.

When does saving nature make “cents”?

Fifty football pitches worth of forest were apparently lost every minute between 2000 and 2012 according to a recent paper by Matt Hansen et al.  And there is little reason to expect this to be different today.  This tremendous pace of forest loss is mostly driven by the clearance of land for agriculture, yet comes at a tremendous cost to the other benefits that people obtain from forests, including carbon sequestration, water purification, and biodiversity.

In a new primer for PLoS Biology – think tutorial more than review – we deliver an overview of the global challenge of reconciling forest conservation with land clearance for agriculture.  We explain how the economic valuation of ecosystem services can provide a way to choose between allocating land to either conservation or development, highlighting a new paper in PLoS Biology by Roman Carrasco and colleagues.  In their paper, Carrasco et al. test how different scenarios of global agricultural production might trade off against the multiple ecosystem services delivered by tropical forests.  They find that the value of those services destroyed by deforestation exceeds the economic benefits of agriculture, except in a few regions if greater yields of high-value crops are eventually realised.  Together, the analytical framework and results of Carrasco et al. should inform the spatial prioritisation of real-world interventions such as REDD+ and can help deliver better environmental and economic outcomes worldwide.  Definitely worth a read!

Finding “hidden” effects of nonnative plant invasion

I seem to have missed this post by Angela Brandt about her great new New Phyt paper. You should check it out below and follow her blog to keep up with all the exciting work she is doing:

Angela J Brandt

In my post-doc work on how colonisation and diversification of plant lineages can have a legacy effect on extant plant communities, we previously showed that understanding evolutionary priority effects is necessary to predict the structure and function of pristine ecological communities. In a paper just published in New Phytologist, we tested whether anthropogenically-driven changes in available habitat and mass immigration (i.e. non-native invasion) eliminate the role of evolutionary priority effects in community assembly. We advanced the theory that radiating lineages can monopolize niche space by showing that evolutionary drivers of community assembly also operate in new habitat created by anthropogenic disturbance. However, we also demonstrated that non-native invasion can erase the otherwise strong role of evolutionary priority effects in shaping native community composition. This work is important and timely because it indicates that effects of human-induced global change on community assembly extend beyond purely ecological dynamics to the ecological consequences of…

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Change (your seed size) fast and multiply

Our latest paper examining the role of life history traits in explaining the vast unevenness of species diversity across the flowering plant Tree of Life has just appeared online at PLoS Biology.  The paper was led by Javi Igea and emerged from a very successful BBSRC DTP rotation project by Eleanor Miller, in collaboration with Alex Papadopulos.

Using the largest available phylogenetic tree of plants coupled with an unparalleled trait dataset, we analysed how seed size and its rate of change across the phylogeny were correlated with the rate of species formation.  Seed size is crucial to plant evolution because it confers adaptation to different environment conditions and influences many other aspects of life history, including dispersal, resistance to stress, and colonisation potential.  We subsequently found that faster rates of seed size change were associated with faster rates of speciation, probably by fostering the appearance of reproductive barriers between lineages.  We also found that smaller-seeded species speciated faster than larger-seeded ones.  These results underscore the importance of morphological traits, and particularly their rate of evolution, in promoting species divergence across one of the largest radiations of organisms on the planet.

Although it has taken a bit longer than we would have liked – no thanks to some poor timing with #BAMMgate – the paper brings together an impressive toolbox of complementary macro-evolutionary analyses to deliver a compelling explanation for one of nature’s enduring mysteries.  Well done all!

Forests feed lake life

Our latest paper has just appeared in Science Advances.  In it, we present widespread evidence that aquatic consumers use terrestrial resources depending on the features of surrounding catchments.  It is really nice to see this out as it caps the food web workshop we organised in Cambridge more than two years ago and includes data we collected during our summer 2014 field campaign.  There’s a nice write up of the work put out by our friends at the Cary Institute.

The work emerged out of our forest fuel fish growth story, which hinted that there can be a lot of variation in the extent to which lake food webs use terrestrially derived material, depending on the features of the surrounding catchments.  With funding from a NERC collaborative grant, our new paper managed to assemble the largest dataset to date of the isotopic composition of zooplankton and their associated food webs from across 147 lakes spanning the boreal to subtropics.  Our aim was to address the use of terrestrial resource in lake food webs once and for all.

Algae and land plants differ in their assimilation of heavy versus light forms of atoms such as carbon, allowing the ratios between these two forms to be used as dietary tracers.  Using these isotopic signatures, we discovered that half of all the zooplankton samples we amassed were comprised of at least 42% terrestrially derived material, but this was underpinned by large variation ranging from 11 to 83%.  Using some awfully complex stats, we go on to show that terrestrial support of zooplankton was generally greatest in lakes with long shorelines and surrounded by dense vegetation and rich soils.  This work now explains the large variation in terrestrial resource use by aquatic food webs and delivers a major advance towards resolving the ‘controversy’ around this process.

Rewinding the Tape of Life

Journal of Ecology Blog

If evolution happened anew, what would the present-day plant world look like?  That is, would the randomized processes that govern evolutionary change tell a different story? And particularly for plants which are sessile organisms, is the starting point of ‘who gets there first’ the most important of all?

Priority effects – the order and timing of species arrival into local communities – can affect ecological community structure and functioning, with profound effects for species persistence and ecological interactions (Chase et al., 2000; van de Voorde et al., 2011). As such, the arrival of different species at different times can dramatically alter the evolutionary tapestry of any given system on ecological time frames, but also in evolutionary time. In particular, the diversification of early arriving species can pre-empt available niche space to prevent the establishment, dominance or diversification of species that arrive later on down the road.

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The future of environmentally-friendly farming?

Our first paper on the agri-environment has just appeared in this month’s issue of PLoS Biology.  This is an important piece for us as it provides a foundation for empirical work being carried out by several group members.

The paper essentially makes three main points.  The first is that we spend a lot more money subsidizing farming than trying to mitigate its environmental impacts.  We’ve tried to plot this out below.  What you can clearly see is that the purple (mitigation expenditure) is nearly invisible relative to what is spent on subsidizing farming (shown in the orange slices).

Financial support to farmers from taxpayers and consumers associated with agricultural policies as a proportion of the total value of agricultural production (VoP) at the farm gate.

The figure now provides what is essentially a map of the ‘perversity‘ of agricultural subsidies – showing where we spend money to do things that are often bad for the environment and costly to the economy.  A first step in reducing conflict between agriculture and the natural environment would be to do away with the subsidies in orange.

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New multi-lake experiment launched

It has been a busy summer for our NERC-funded project RELATED (that stands for Restoring Ecosystems by Linking Aquatic and Terrestrial Ecological Dynamics).  The project aims to test experimentally whether the productivity of aquatic food webs increases with the quantity and quality of terrestrial organic matter deposited in nearshore delta habitats.  It builds on our previous work that showed forests fuel the growth of juvenile fish by subsidizing the base of the aquatic food web.  RELATED will also feature much more work on unlocking the microbial ‘black box’ at the base of the food web as well as better understanding how greenhouse gas emissions might change with surrounding vegetation.  Inland waters are major sources of atmospheric carbon and predicting their responses to future change is of major interest (some great recent work here, here, and here).

Experiment behind the beautiful Living with Lakes Centre

New experiment behind the beautiful Living with Lakes Centre

We’ve now just finished launching the experimental platform behind RELATED.  Over the last 8 weeks, we’ve had a team of 8+ working tirelessly to submerge artificial lake sediments in 3 lakes.  This has involved collecting, mulching, and sifting organic and inorganic materials, mixing these at an industrial scale, and outfitting nearly 300 mesocosms with the appropriate sampling gear.  By replicating our experiment in 3 different lakes, we’ll be able to study terrestrial-aquatic linkages along gradients in eutrophication and climate change – the main drivers of change in the world’s inland waters.  We’ve also had excellent student help from Laurentian University’s School of Architecture work to design and build a network of sampling platforms that will allow us to work without disturbing our sediments.

Artificial sediments with increasing organics from left to right.

Artificial sediments with increasing organics from left to right.

Here’s the main team celebrating the deployment of the experiment in Ramsey Lake: