The 7th of December 2009 marks the beginning of the United Nations climate change conference in Copenhagen, also known as COP15 and it is billed as an opportunity for world governments to figure out some real, effective actions to take in the fight against climate change. Because climate change affects everyone, even pests!
The effects of climate change on pests and their behaviours have been studied for many years. It is possible, for example, to predict how a change in temperature as small as 5°C can dramatically change pest problems based on previously observed behavious.
So let’s take a look at what climate change is doing to three very common pests: cockroaches, moths and rodents.
We all know what cockroaches are, and most of us have heard that they are one of the few creatures which could survive a nuclear holocaust (which may or may not strictly be true). The most common species of cockroach in England are the German and Oriental cockroaches, but others including the American and the brown-branded types, are also found.
Adult cockroaches can live from four to 14 months, and in their lifetimes, standard female cockroaches can produce up to 50 egg sacs, called oothecae. Each ootheca can hold between 12 and 30 eggs, meaning a female can produce 1500 eggs over the course of her life.
The effects of climate change on cockroaches
Interestingly, cockroaches release methane every 15 minutes, putting them amongst the biggest greenhouse emitters – even more than cattle or termites. This is the most efficient bio-fuel reactor that exists and warrants further research.
Because their reproduction is temperature-sensitive, cockroaches are very easily affected by rising temperatures. So the hotter the temperature – the faster they breed and the faster they can spread diseases, contaminate foodstuffs and damage goods.
For most species of cockroach, breeding conditions begin at 20°C which is the average temperature of London in June. At that temperature, the hatching cycle of a cockroaches eggs is 94 days, or just over three months.
Increase the temperature by 5°C, however, and the hatching cycle is halved. Increase by another 5°C, and you’ve reached the optimum temperature for cockroach breeding; the hatching cycle is halved again, and it only takes 24 days for the eggs to hatch.
The current increase in global temperatures, although relatively small, is nonetheless already affecting cockroach populations.
In Sydney, for instance, the German cockroach (which had long been the most common of the Australian cockroaches) has disappeared and been replaced by the Australian house cockroach, an insect that normally likes warmer climes.
It is said that moths can be distinguished from butterflies by:
- using the “butterflies fly by day and moths by night” adage or
- observing their beautiful colours (or lack thereof) or
- looking at the way they hold their wings in repose (with butterflies holding their wings together and above their bodies and moths hold their wings apart and to their sides) or
- looking at the antennae: a butterfly’s end in a club shape and a moth’s do not.
These identifiers are generally reliable, but they each have their own exceptions – like the many day-flying moths or the brightly coloured Elephant Hawk Moth.
There are over 120,000 species of moths worldwide, 2500 of which can call the UK home.
Many moths damage and contaminate stored food products and are found in houses, bakeries or warehouses. The more infamous clothes eating moths (or rather their larvae) can eat carpets and other household items in addition to clothing.
The effects of climate change on moths
The most dramatic effect on moths is the migration of the Oak Processionary moth. The moth lays its eggs in oak trees, where as a caterpillar it eats the foliage. The caterpillars have poisonous hairs along their backs, and on humans, its effects range from breathing difficulties to more severe allergic reactions. As temperatures in Europe rise, it has moved from the Mediterranean regions of Europe north. The source data from the Netherlands below shows overall sightings (by date – where blue is the end of the year) and how they have been moving north to traditionally cooler climates.
Like cockroaches, moths can also have a significant impact on global warming themselves.
Following an infestation of Siberian silk moths, affected forests can be more susceptible to forest fires because of dry, dead vegetation. The outbreaks have also been linked with increased microbial activity in the soil, and an increase in such activity releases more carbon dioxide. This image shows how much damage was caused by one such attack.
Rodents are very common and incredibly adaptable. About 40% of mammal species are rodents, and they are found on all continents apart from Antarctica. They eat everything humans do, and they even thrive on contaminated food and water. Rodents consume 20% of the world’s growing and stored grain, eating 13% of the USA’s grain and up to 75% in some African countries.
They are also great swimmers, which is why flooded areas often find themselves fighting a mischief of rats on top of dealing with the waters.
The 22 counties surrounding Dongting Lake in China found this was the case when they were invaded by an estimated 2 billion rats after floodwaters burst in June 2008.
The effects of climate change on rodents
Given that they live so well in contaminated, waterlogged areas, it’s unsurprising that wild rodents can carry so many diseases. Leptospirosis, for example, is a major vector borne disease that needs to be considered following natural disasters.
Climate change causes wild variations in weather patterns, often bringing long periods of drought followed by a warm, early spring. These are ideal conditions for these hardy animals, as it increases their mating season and the conditions in which they – and little else – can survive:
- In 1994, India suffered the re-emergence of The Plague following a blistering summer.
- Rodent populations in southern Africa exploded after torrential rains in 1993 and 1994.
- The United States recorded the first-ever outbreak of hantavirus pulmonary syndrome in the wake of 1991 and 1992’s El Niño phenomenon.
Climate change causes enough anxiety with the natural phenomena it directly affects, such as the occurrence of severe hurricanes, snow and ice melting too quickly for flora and fauna to adjust, and even the brutality of blizzards. When government representatives meet at COP15, they are likely to be discussing these issues, which is helpful and will ideally spur global action.
Concentrating on the prevalence and obvious danger of the primary consequences, however, means we could risk ignoring and being unintentionally ill-prepared for the secondary consequences. Because we’re not thinking about things like pest behaviour and populations, we may find ourselves unprepared to deal with them when they happen. Pest awareness is important, be vigilant.