COP21 Guest blog – Dr. Chris Hassall, evolutionary ecologist

Chris Hassall is an evolutionary ecologist working on human impacts on ecological systems (with a focus on freshwater ecology and climate change) and large-scale evolutionary patterns (with a focus on invertebrates as model systems to look at ageing and mimicry) at the University of Leeds.


The focus of the negotiations at COP21 will be on avoiding dangerous climate change to ensure the planet remains suitable for people. However, in striving for this goal we will also provide a wide array of benefits to the other biological organisms with which we share the world. My research over the past decade has focused on trying to understand the biological implications of climate change, and I have focused on the role that changing environmental temperature plays in driving changes in insect populations.

Insects form a significant percentage of all animals. Indeed, as Robert May, the former President of the Royal Society once quipped: “…to a first approximation all species are insects“. We are fed upon by mosquitoes, our crops are munched by caterpillars, and our homes are gnawed by termites. However, we are also reliant upon bees and other pollinators for our food, and many other insects consume the pests that would otherwise damage our crops. Understanding this complex network of beneficial and malefic species requires not only an understanding of how they interact, but also how climate change will influence their distributions, numbers, and behaviour.


Early on in my career I became fascinated by one group of insects in particular: the dragonflies. These animals have been considered traditionally to be indicators of clean water by Native American peoples – a link that has also been made through the use of various dragonfly groups as barometers of ecological water quality in the Water Framework Directive. Dragonflies are an important part of the environment as they live for most of their lives in the water as predatory larvae (sometimes up to four or five years) before emerging as the winged adult with which most of us are familiar. This means that their health reflects the quality of aquatic and terrestrial environments. The dragonflies evolved in the tropics and so are well adapted to warmer temperatures, meaning that as the environment becomes warmer under climate change they are one of the first groups that are able to take advantage. My work, published in 2007, was the first to demonstrate that aquatic species are emerging earlier in the year in response to climate change. DRAGONFLY

Since then I have worked on species that are expanding their ranges under climate change, particularly the small red-eyed damselfly.  Work in which I was involved has suggested that the number of animals coming into the UK is far greater than expected, which runs counter to our earlier assumption that species extend their ranges through the colonisation of new habitats by a small number of pioneers. I have also demonstrated in a number of species that the animals at the leading edge of an expanding range tend to have far more developed flight equipment (wings and muscles). This sort of information is important in our understanding of how other species might respond to climate change, and how animals may evolve in a dynamic world.


A second group of insects with which I work is the hoverflies.  These small flies are often seen buzzing around flowers in our gardens where they pollinate plants, and there are around 270 species in the UK. My current research, funded by an EU Marie Curie Fellowship, is investigating the consequences of climate change for this group of insects, with a focus on when they emerge. This is particularly important in the case of pollinators like the hoverflies because if the pollinator does not emerge at the same time as the plant that requires it then both the plant and the insect may suffer. We call this problem “decoupling”, and we know that it is already happening in other species such as birds that rely on particular caterpillars, and aquatic crustaceans that rely on particular algae.hoverfly

Along with pollination, hoverflies are also known to mimic various species of stinging wasps and bees. In the group of photos to the right there are five stinging insects and seven harmless hoverflies. As you can tell, this mimicry poses a problem for the animals that eat hoverflies, as those predators need to be able to distinguish the harmless hoverflies from these stinging insects. My EU-funded research is investigating how the relative changes in the distributions of the wasps, bees, and hoverflies might further confuse predators by altering the locations and times of year when the different species occur. Hence my current work focuses not only on the environmental and conservation aspects of climate change, but also uses climate change as a “natural experiment” to explore more fundamental evolutionary processes.