Category Archives: Paper of the Week

Fishing for Invaders

Image Credit: California Department of Fish and Wildlife, CC BY 2.0, Image Cropped

Angling as a source of non-native freshwater fish: a European review (2019) Carpio, De Miguel, Oteros, Hillstrom & Tortosa, Biological Invasions, doi.org/10.1007/s10530-019-02042-5

The Crux

People love fishing. It’s an intrinsic part of some people’s lives, whether as a livelihood or a past-time. People who have grown up fishing often have specific species that they enjoy fishing for. Nothing wrong with that.

Yet people’s desire to go after one fish species will often lead them to move that species around. This can happen on a small scale, with people moving a species from one lake to another slightly closer to their homes. Or it can happen on a massive one, with a species being transported to new continents.

This has shaped entire freshwater communities in modern-day Europe, where 195 species now reside that have no natural range in the continent. Most of these have been introduced since the nineteenth century, which is around the time that fishing became a popular recreational activity. This week’s authors wanted to find out what the role of recreational fishing was in shaping the make-up of today’s invasive freshwater fish populations in Europe.

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Hibernating and Mating

Male echidna must stay on the move to find females before other males do (Image Credit: JKMelville, CC BY-SA 3.0, Image Cropped)
Energetics meets sexual conflict: The phenology of hibernation in Tasmanian echidnas (2019) Nicol et al., Functional Ecology, https://doi.org/10.1111/1365-2435.13447

The Crux

Seasonality (i.e. the change in season throughout the course of the year) has huge impacts on the lives of animals that live in temperate habitats. The change in season is associated with changes in food availability, and as such some animals hibernate through the tough winter months and wait until the food and warmer weather comes back. Another aspect of an animal’s life impacted by seasonality is the breeding season, as animals living in temperate habitats must time their breeding around the winter months, while animals in tropical habitats can breed year-round.

Within a single species the timing of hibernation may be affected by the different energetic and reproductive needs of the different sexes. Females may start hibernating later than males because they have to store more energy for their pregnancy and lactation, while males may emerge from hibernation earlier than females to establish territories and increase their chance of mating. Tasmanian echidnas (Tachyglossus aculeatus) exhibit markedly different hibernation patterns among the sexes, and the authors of today’s study wanted to know if these differences are due to where they live or whether they are inherent to the species itself.

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Are the Combined Effects of Human Development Worse Than the Sum of Their Parts?

Decreases in river discharge can negatively affect fish like this sucker, but what happens when they’re compounded by local changes in land use? (Image Credit: Hotash, CC BY 2.0, Image Cropped)

Anthropogenic land-use change intensifies the effect of lows flows on stream fishes (2019) Walker, Girard, Alford & Walters, Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.13517

The Crux

Human activity can create a lot of different problems for the world’s ecosystems. These problems can impact an ecosystem simultaneously, often in different ways. For instance, a warming climate might push some species further towards the poles, but human structures like factories or mines might impede their dispersal. It’s relatively easy to study the effect of any one stressor that we place on a species, but looking at the interaction of multiple human-caused stressors is more difficult.

Take freshwater ecosystems. A warming climate means that there’s less snow and more rain in the winter, which reduces the river’s flow (or discharge) in summer. At the same time, nearby human construction can reduce nearby plant life, which in turn increases the amount of sediment washed into a river and lowers water quality. But do the two effects combined simply equal the sum of their parts, or does that combination make the total effect on local species even worse?

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The Early Mouse Gets the Cheese

For small animals like the mouse, predators are a constant concern (Image Credit: Jess, CC BY-NC 2.0)

Maximising survival by shifting the daily timing of activity (2019) van der Vinne et al., Ecology Letters, https://doi.org/10.1111/ele.13404

The Crux

All animals need to eat food to survive and maintain their energy balance, but unlike us they can’t just order a pizza and have the food brought to them. They must always forage for food themselves, and every time that they do they expose themselves to predators. Small mammals like mice balance this trade-off by foraging for food at night, when their risk of predation is lowest.

One interesting strategy that mice can employ is to switch their foraging from the nighttime to the day, if they cannot get enough resources during the night or if their nighttime predation risk increases. The authors of today’s paper wanted to develop a model to predict under what conditions these temporal switches would occur, a model which they then tested with mice in the field.

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A Review of Netflix’s Our Planet as a Conservation Tool

The new Attenborough-narrated Netflix series Our Planet aimed to put threats to the environment at its forefront. So how well did it do? (Image Credit: Mikedixson, CC BY-SA 3.0, Image Cropped)

Nature documentaries and saving nature: Reflections on the new Netflix series Our Planet (2019) Jones, Thomas-Walters, Rust & VerissimoPeople and Nature, https://doi.org/10.1002/pan3.10052

The Crux

Nature documentaries have long been the starting point for many an ecologist. They’re the reason that David Attenborough has long been so idolised among lovers of nature. But whether or not they actually work as a conservation tool has always been a little more difficult to say. Additionally, while they’ve long showed the wonder of animals, plants, insects and everything in between, many have shied away from the damage that humans have inflicted on the planet. This week’s authors wanted to examine Netflix’s latest move into nature documentaries, Our Planet, and see if it delivered on their promise to showcase the anthropogenic dangers that ecosystems face today.

What They Did

The methods here were pretty simple. The scripts for Our Planet, as well as three other recent David Attenborough led documentaries (Blue Planet, Blue Planet II and Dynasties) were analysed. The percentage of the word count which dealt with threats to the natural world was calculated, as well that which dealt with success stories regarding species and ecosystem conservation.

What They Found

Our Planet did spend more time talking about the dangers to the planet than the other three documentaries, with only Blue Planet II having a similar word count. Blue Planet II  actually spent more time on conservation success stories than Our Planet (although most of this was packed into one final episode). One of the issues present though was that the visuals remain largely unchanged, with human impact on nature largely confined to Attenborough’s narration. This may have lessened the show’s impact on viewers and given the impression of nature as constantly stunning and untouched.

The constant portrayal of nature as untouched by humans can give a false impression of how brutal the effects of fragmentation and habitat disturbance are

The constant portrayal of nature as untouched by humans can give a false impression of how brutal the effects of fragmentation and habitat disturbance are (Image Credit: Sam Perrin, NTNU, CC BY-SA 2.0)

Problems?

There aren’t problems with the study itself so much as with the questions it posts. Sure, Our Planet spends more time talking about issues like climate change and deforestation, but does that translate to a tangible effect? It’s extremely difficult to study the effect of nature documentaries on conservation efforts. One tangible example that the paper brings up is the UK policy change on marine plastics, which is somewhat credited to the final episode of Blue Planet II. Even then, how much the documentary actually played into the policy decision is debatable.

So What?

It’s a problem faced by nature filmmakers everywhere – you want to show the truth, but are worried that anything too depressing or severe will reduce viewership. And as stated above, even if documentaries do start to bring the impact of humans on nature more front and center, it’s difficult to know whether this aids conservation efforts. For starters, people who watch nature documentaries are likely to already have some sort of interest in nature, which makes viewers a biased sampling pool. The good news is that there are a growing number of methods which could be used to deal with these issues. Hopefully we will start to see some tangible effect of the work of Attenborough and the rest of the nature documentary industry some day soon.

Helping the Little Guy

Animals often compete with one another for food, but sometimes their actions can actually help other animals (Image Credit: Dennis Jarvis, CC BY-SA 3.0, Image Cropped)

Food and habitat provisions jointly determine competitive and facilitative interactions among distantly related herbivores (2019) Pan et al., Ecology Letters, https://doi.org/10.1111/1365-2435.13456

The Crux

Community structure, or the makeup of species within a given habitat, is largely determined by the interactions between the organisms that feed on plants. As such, the effects that different herbivores have on one another may impact how they feed, which would then feed back into which plants that are consumed, which would impact community structure. When one herbivore has a positive effect on the feeding of another, this is called facilitation.

Classically, facilitation has been studied as a one-way interaction (Species A facilitating Species B), but this ignores the reality of natural systems, where any interaction between species has the potential to act both ways. Today’s study investigated three different herbivores to investigate how they may interact with and/or facilitate one another.

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Going Beyond Range Size in Analysing Extinction Risk

Animals of wildly different sizes may have different likelihoods of extinction, but it could all depend on their range sizes (Image Credit: Harvey Barrison, CC BY-SA 2.0, Image Cropped)

Constraints on vertebrate range size predict extinction risk (2019) Newsome et al., Global Ecology and Biogeography, http://doi/epdf/10.1111/geb.1309

The Crux

To act to prevent a species going extinct, we have to know that it’s at risk of extinction. Ecologists and conservationists simply don’t have the time or resources to make sure that all species remain safe. So having reliable methods of predicting species extinction risk is crucial.

On a global scale, the relationship between a species size and the area that it is found in (geographical range) has been studied intensively since ecology’s inception, both in existing and prehistoric species. Initial research showed that in general, the larger a species is, the larger its range size needed to be, with large species that had relatively smaller range sizes more prone to extinction. However more recent work has shown (naturally) that there are exceptions to this, with mammals viable range size actually decreasing up to a certain ‘breakpoint’, after which the size grows again.

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