All The Small Things

This group of animals has been somewhat overlooked both by conservation organisations and the public.

Much has been written about the decline of large, charismatic predators and the effect their loss has on ecosystems. However, a new study decided instead to examine the impact of humans on significantly smaller but no less important species – invertebrates (animals without a backbone).

This group of animals has been somewhat overlooked both by conservation organisations and the public. The IUCN has assessed less than one percent of the 1.4 million named species of invertebrates. The study, published in Science and led by scientists from University College London, Stanford, and the University of California Santa Barbara, made a surprising finding. Over a 30 year period, during which the human population has doubled to over 7 billion, invertebrate numbers have decreased by an average of 45%.

Dr Ben Collen, one of the study’s authors, said: “We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient. While we don’t fully understand what the long-term impact of these declining numbers will be, currently we are in the potentially dangerous position of losing integral parts of ecosystems without knowing what roles they play within it. Prevention of further declines will require us to better understand what species are winning and losing in the fight for survival and from studying the winners, apply what we learn to improve conservation projects. We also need to develop predictive tools for modelling the impact of changes to the ecosystem so we can prioritise conservation efforts, working with governments globally to create supportive policy to reverse the worrying trends we are seeing.”

The lead author, Professor Rodolfo Dirzo, added: “Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission. Who would have thought that just defaunation would have all these dramatic consequences, but it can be a vicious circle. We tend to think about extinction as loss of a species from the face of Earth, and that’s very important, but there’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well. Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is noncryptic because of the increasingly obvious consequences to the planet and to human well-being.”

The decrease is due to two main factors – habitat loss and climate disruption on a global scale. In the UK alone, the scientists noted, the areas inhabited by common insects such as beetles, butterflies, wasps and bees saw a 30-60% decline over the last 40 years. Invertebrate declines are worrying because of the enormous benefits they provide to human society. Insect pollination is required for 75% of all the world’s food crops, pest control by native insects is estimated to be worth US$4.5 billion every year in the US alone, and insects play an important role in nutrient cycling.

We must lessen our impact on the planet we dominate so that we don’t lose the essential services that insects so conveniently provide.

Tags: CoccinellaInvertebratesladybird