Rivers have played a monumental role in determining where people live. Their importance in providing water, transportation and a raft of other ecosystem services has meant that even today most of the world’s largest cities are situated close to a major source of freshwater, from Sydney to Delhi, Quebec to Karachi.
Yet despite their role in our history, urban rivers today are often facing increasing levels of pollution as a result of human activity. As well as often being a huge tourist drawcard, and an ongoing resource for fishers, joggers and portable BBQ toters, freshwater ecosystems carry a disproportionate number of aquatic species, which makes this trend increasingly worrying.
After meeting at last year’s British Ecological Society Annual Meeting, I got in touch with Dr. Cecilia Medupin, a freshwater ecologist at the University of Manchester. Cecilia works to increase peoples understanding of rivers, including the project Our Rivers, Our City. I asked Cecilia abut our connection with rivers, the challenges they face, and how to inspire research and change in urban rivers.
Image Credit: Jacob Biewer, Sankey et al., 2015
The charisma of enormous, slashing teeth is undeniable. Despite the fact that there are a myriad of fascinating prehistoric carnivores, the big mammals that the documentaries, big-budget films and kid’s shows seem to come back to are the sabre-toothed carnivores. Massive slashing teeth are actually a trait that has popped up a lot over the course of the Earth’s history, with at least three different groups of cat or cat-like mammal evolving them as a hunting mechanism. As well as a fish.
Image Credit: Manfred Antranias Zimmer, Pixabay licence, Image Cropped
Invasion of freshwater ecosystems is promoted by network connectivity to hotspots of human activity (2019) Chapman et al., Global Ecology and Biogeography, https://doi.org/10.1111/geb.13051
The spread of invasive species throughout freshwater ecosystems is a topic we’ve looked at before on Ecology for the Masses. In a previous paper breakdown we talked about how recreational is heavily responsible for the presence of non-native fish at a European scale.
Our paper this week takes a more local approach. Can we predict the presence of non-native birds, invertebrates and fish by looking at the presence of human activity, and where that human activity is present?
Increased urbanisation may have a negative effect on the richness of moth species like this Vine’s Rustic, but it depends on what scale we consider richness (Image Credit: Patrick Clement, CC BY 2.0, Image Cropped)
Urbanization drives cross-taxon declines in abundance and diversity at multiple spatial scales (2019) Piano et al., Global Change Biology, https://doi.org/10.1111/gcb.14934
You would think that the effect of building a whole lot of stuff on something’s habitat would have a negative effect on just about anything. But building a whole lot of human stuff (maybe let’s retain a modicum of science-ness and call it urbanisation) hasn’t always been shown to be necessarily bad for species. There are a lot of studies out there which show that urbanisation is can be a negative for biodiversity (which makes sense, since for starters it generally breaks up habitat patches and introduces a whole lot more pollutants). But there are also studies showing that urbanisation can increase biodiversity.
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
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.
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
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?
Radiation can have extremely negative effects on an individual. But is it as easy to measure its effects on an entire population? (Image Credit: Hnapel, CC BY-SA 4.0, Image Cropped)
Variation in chronic radiation exposure does not drive life history divergence among Daphnia populations across the Chernobyl Exclusion Zone (2019) Goodman et al., Ecology and Evolution, DOI: 10.1002/ece3.4931
As anyone who has recently watched HBO’s Chernobyl can tell you, large doses of radiation are capable of doing some pretty serious damage to an organism. But whilst examining the effect of radiation on an individual might be simple, monitoring those effects on a population can be difficult. Whilst radiation negatively effects fitness, it can also help individuals with higher radiation tolerance to reproduce and dominate within the population of a single species, making it difficult to monitor the exact effects of radiation on that population. If a population is filled with only those who were strong enough to survive, you don’t get an idea of the variation in the radiation’s effects.
This week’s researchers tried to break through that problem by looking at different populations of a water flea in Chernobyl’s Exclusion Zone (CEZ) – the area still barred from entry in eastern Europe.
Image Credit: ulleo, Pixabay licence, Image Cropped
Natural selection favors a larger eye in response to increased competition in natural populations of a vertebrate (2019) Beston & Walsh, Functional Ecology, doi: 10.1111/1365-2435.13334
Studying the evolution of traits in response to selection pressure often helps us understand why species look and act the way they do. Selection pressure can include the need to find food before other members of your species, or the need to escape predation.
But what happens when improving your ability to obtain resources also means you’re more vulnerable to predation? Which will win out? This paper looks at a small species of freshwater fish, Rivulus hartii, and determines which of the two pressures contributes most to the evolution of the size of their eye.