Climate change interferes with our use of animals to judge water quality

Background: Water quality is measured in a number of different ways: measuring levels of chemicals and pollutants, measuring temperature and other physical parameters, and monitoring the animals and plants that are living in the water. The theory is that the animals and plants living in the water have certain requirements of their habitat (particularly a need for clean water) and so you can use the presence of certain “fussy” animal groups as a proxy for water quality. The problem is that, under climate change, species are moving around as environmental conditions – especially temperature – changes.  This means that changes in the animal and plant communities at a given site might give the appearance of an increase in water quality while actually the arrival of new species is simply the result of climate change.

What we did: I analysed an extensive dataset of British dragonfly and damselfly (known collectively as the “Odonata”) sightings to look for a pattern of geographical movement since 1960.  Dragonflies and damselflies are an important group in biological water quality monitoring, as they are particularly sensitive to pollution.  I found that the patterns of water quality that would be detected using Odonata at a generic site would appear to change over time with the changes in Odonata communities, independent of any changes in water quality.

Importance: Biological communities are used extensively in the monitoring of freshwaters and this research emphasises the need to take distributional shifts that occur as a result of climate change into account when using this method. It is likely that water quality is improving, with better treatment of wastewater and better enforcement of environmental regulation, but accurate monitoring is the key to continuing improvement. Secondly, this paper demonstrates once more the fact that Odonata are responding to climate change.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “The impact of climate-induced distributional changes on the validity of biological water quality metrics”, was published in the journal Environmental Monitoring and Assessment in 2010. You can find this paper online at the publisher, or on Figshare.

Image credit: Tambako the Jaguar, CC BY-ND 2.0,

It’s hard to predict how many species a pond might contain…

Background:  Ponds have been identified as a very important habitat in the landscape.  They enhance regional biodiversity, help control floodwater, reduce pollution in run-off from agricultural and urban land, and provide greenspace and biodiversity in urban environments.  However, because of their small size (typically less than two hectares), they have been neglected by scientists until the last couple of decades.

What we did: This study used a large dataset of 454 ponds that had been surveyed in the north of England to identify all of the invertebrate and plant species that inhabited them. A wide range of physical, chemical and biological variables were also measured and, as the title of the paper suggests, we investigated which of these variables were related to the species richness of different plant and animal taxa. We were able to predict a reasonable amount of the diversity of invertebrates in general, but predictions varied between groups of invertebrates. In general, more shade and a history of drying up reduced the diversity of all groups.

Importance: It has been shown that landowners and managers tend to manage ponds and other natural resources using “received knowledge”. in other words, there is little evidence base for such management.  Our study demonstrated a few important relationships which can be used to inform this kind of management.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Environmental correlates of plant and invertebrate species richness in ponds”, was published in the journal Biodiversity and Conservation in 2011. You can find this paper online at the publisher, or on Figshare.

Image credit: That’s one of mine, CC-BY 3.0.

Ponds are dynamic habitats, which makes it tough to conserve biodiversity…

Background:  When an area is designated as a site for conservation or special scientific interest that is usually because one or more species of interest have been found or the community as a whole is unique or exceptional. However, the implicit assumption in this approach is that if you come back tomorrow then those species or that community will still be present. If the habitat is dynamic, with frequent population-level extinctions and colonisations, then it may be that this assumption does not hold. Pond ecosystems represent one case where the habitats are small and relatively easily affected by external variables and which may, as a result, vary in their conservation value over time.

What we did: Andrew Hull and Jim Hollinshead have been monitoring ponds in Cheshire (northwest England) for almost 20 years. A set of 51 ponds were surveyed in 1995/6 and again in 2005, meaning that we can test whether or not over this 10-year period there was any change in the conservation value of the ponds. Pond surveys recorded all plant and macroinvertebrate (i.e. invertebrates larger than about 1mm, which was the size of the mesh of the net) species in the ponds and we compared (i) the diversity, and (ii) the conservation value of the ponds between the two surveys. Plants showed similar levels of diversity in both surveys, so highly-diverse ponds in the first survey remained that way in the second. However, invertebrate diversity was not correlated between surveys, meaning that species rich ponds in the first survey did not necessarily remain that way. For both groups there was not correlation between conservation value (calculated based on the rarity of the species in the community) in survey 1 compared to survey 2.

Importance: Ponds are highly variable ecosystems and that is one of the reasons that they support such a wide range of species on a landscape scale. However, it seems that this variability may make it difficult to conserve them adequately, since conservation value is changing over time. This finding supports the conservation of pond clusters, rather than individual sites, which are more likely to contain a stable species pool.

This is part of a series of short lay summaries that describe the technical publications I have authored. This paper, entitled “Temporal dynamics of aquatic communities and implications for pond conservation”, was published in the journal Biodiversity and Conservation in 2012. You can find this paper online at the publisher, or on Figshare.

Image credit: Alison Benbow, CC BY 2.0,