Image credit: Muséum de Toulouse, CC BY-SA 4.0, via Wikimedia Commons
Top-down response to spatial variation in productivity and bottom-up response to temporal variation in productivity in a long-term study of desert ants (2022) Gibb et al., Biology Letters, https://doi.org/10.1098/rsbl.2022.0314
Ecosystem productivity can tell us a lot about how an ecosystem functions. The more productive an ecosystem is, the more life it can support. But productivity doesn’t just affect the diversity or number of species within an ecosystem, it affects how those species interact, from the large carnivores you find at the upper levels, to the plants and bacteria down the ‘bottom’.
Within ecosystems, the strength of a top-down process (something influencing those upper levels) vs. a bottom-up process (something influencing the lower levels) depends on how much primary productivity there is. Primary production occurs when a species makes its own energy instead of eating something else, and when there is a lot of it going around, it often allows the carnivores at the upper trophic levels to suppress the population numbers of herbivores. That means that while a bottom-up process may end up affecting the herbivores, a top-down process (like the hunting of carnivores) might impact the entire ecosystem.
On the other side of the spectrum, when there is little primary productivity, there aren’t usually as many carnivores suppressing the herbivore populations. A bottom-up process will increase herbivore numbers, making these bottom-up processes more important in these low-productivity systems. This is known as the Exploitation Ecosystem Hypothesis (EEH).
A young octopus (Graneledone verrucosa) moves across the seafloor. Observed during the Okeanos Explorer Northeast U.S. Canyons 2013 expedition. (Image Credit: NOAA Ocean Exploration & Research, CC BY-SA 2.0, Image cropped)
In nature every death brings new life. A fascinating example are whale-falls: when a whale dies, its carcass will sink down to the ocean floor where it creates a unique ecosystem for bottom-dwelling organisms. Whales’ bodies can weigh up to 200 tons and contain massive amounts of fat and proteins. When a dead whale reaches the ocean floor it brings a lot of resources to an environment which is usually limited by food availability. The fortunate creatures experiencing the whale-fall welcome such a great source of nutrition, and use up everything they can, until the last vertebra is decomposed.
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: hbieser, Pixabay Licence, Image Cropped
Introduced herbivores restore Late Pleistocene ecological functions (2020) Lundgren et al., PNAS, https://doi.org/10.1073/pnas.1915769117
The fauna of the Pleistocene (also known as the Ice Age) was not that dissimilar to the communities of animals which inhabit our planet now. However, many more large land mammals inhabited all kinds of ecosystems. By the end of the Pleistocene, many of them were extinct, mainly due to climate change impacts (glaciers got larger and restricted their ragne) and prehistoric human impacts like over-hunting, habitat alteration, and introduction of new diseases. The decline of large-bodied herbivores in the Late Pleistocene (LP from here on) led to many ecological changes including reduced nutrient cycling and dispersal, reduced primary productivity, increased wildfire frequency and intensity, and altered vegetation structure. These changes have become our norm.
Scientists usually study species introduction under the premise that they are ecologically novel. However, the introduction of large herbivores has been found to drive changes in the environment, potentially restoring or introducing novel ecological functions similar to pre-extinction Late Pleistocene conditions. This week’s researchers wanted to investigate what sort of role introduced mammals played in restoring ecological interactions by investigating their functional similarity with LP species.
Mapping co-benefits for carbon storage and biodiversity to inform conservation policy and action (2019) Soto-Navarro et al., Philosophical Transactions of the Royal Society B, https://doi.org/10.1098/rstb.2019.0128
With the world under so many anthropogenic pressures simultaneously, trying to come up with management solutions for different issues can be a problem. Climate change and biodiversity are a great example. Storing carbon is a great way to reduce the effects of climate change, and increasing the range of forests worldwide is a great way to increase carbon storage. Yet the sort of forests that store carbon most efficiently are often poor at promoting biodiversity. They are largely made up of very similar trees, while forests that include brush, scrubs, and other layers often store less carbon, but house more biodiverse communities.
As such, finding areas that are prime specimens for a) storing carbon and b) biodiversity conservation are incredibly important, so that managers at every level (from park rangers right up to the Intergovernmental Panel on Climate Change) can know where interests overlap, and adjust plans accordingly.
Image Credit: Ray Bilcliff, Pexels licence, Image Cropped
We get a lot of fun and strange search terms which lead people to Ecology for the Masses. So inspired by Captain Awkward’s segment ‘It Came From the Search Terms‘, let’s have a look at some of the weirder questions that led people to this site and see if we can provide some answers. Spelling mistakes have been corrected.
Image Credit: Christopher Michel, CC BY 2.0, Image Cropped, Brightened
It’s an image that is ubiquitous in the media when the words ‘climate change’ pop up. The lone polar bear, drifting through the sea on a single ice floe. It is an effective image, evoking emotions like pity, loneliness and general despair for the plight of what has become the flagship species of what seems like the entire Arctic. But is associating the health of an entire ecosystem with one species useful, or dangerous?
Ecological data is constantly being collected worldwide, but how accessible is it? (Image Credit: GBIF, CC BY 4.0, Image Cropped)
This week Trondheim played host to Living Norway, a Norwegian collective that aims to promote FAIR data use and management. It might sound dry from an ecological perspective, but I was told I’d see my supervisor wearing a suit jacket, an opportunity too preposterous to miss. While the latter opportunity was certainly a highlight, the seminar itself proved fascinating, and underlined just how important FAIR data is for ecology, and science in general. So why is it so important, what can we do to help, and why do I keep capitalising FAIR?