Dramatic loss of insect life

A recent study(1) undertaken by researchers from the University of Sydney and University of Queensland in conjunction with the China Academy of Agriculture Sciences has found that biodiversity of insects is threatened worldwide. This recent study reveals dramatic rates of decline that may lead to the extinction of 40% of the world’s insect species over the next few decades. Affected insect groups not only include specialists that occupy particular ecological niches, but also many common and generalist species including butterflies, ground beetles, ladybirds, dragonflies, stoneflies and wild bees. Concurrently, the abundance of a small number of species is increasing; these are all adaptable, generalist species that are occupying the vacant niches left by the ones declining. Among aquatic insects, habitat and dietary generalists, and pollutant-tolerant species are replacing the large biodiversity losses experienced in waters within agricultural and urban settings. The main drivers of species declines appear to be, in order of importance: i) habitat loss as a result of conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change.

For years, biologists and ecologists have been concerned about the worldwide reduction in biodiversity undergone by many terrestrial and aquatic vertebrates, yet scientists have only recently voiced similar concerns about insects. Population declines imply not only less abundance but also a more restricted geographical distribution of species, and represent the first step towards extinction. Much of the blame for biodiversity loss falls on human activities such as habitat loss through deforestation, agricultural expansion and intensification, industrialisation and urbanisation which jointly claimed a 30–50% encroachment on natural ecosystems at the end of the 20th century.

There is compelling evidence that agricultural intensification is the main driver of population declines in birds, insectivorous mammals and insects. In rural landscapes across the globe, the steady removal of natural habitat elements (e.g. hedgerows), elimination of natural drainage systems and other landscape features together with the recurrent use of chemical fertilisers and pesticides negatively affect overall biodiversity.  Recent analyses point to the extensive usage of pesticides as primary factor responsible for the decline of birds in grasslands and aquatic organisms in streams, with other factors contributing to or amplifying their effects to varying extent.

In 2017, a 27-year long population monitoring study revealed a shocking 76% decline in flying insect biomass at several of Germany’s protected areas. Similarly a 2018 study in rainforests of Puerto Rico has reported biomass losses between 98% and 78% for ground-foraging and canopy-dwelling arthropods over a 36-year period. Not unexpectedly the report showed a parallel decline in birds, frogs and lizards at the same areas as a result of invertebrate food shortages. Both studies confirmed the declining trend in flying insects observed a decade earlier in parts of Southern Britain. As insects comprise about two thirds of all terrestrial species on Earth, the above trends confirm that the sixth major extinction event is profoundly impacting life forms on our planet.

The above studies, are in line with previous reports on population declines among numerous insect populations including  butterflies, ground beetles, ladybirds, dragonflies, stoneflies and wild bees in Europe and North America over the past decades. It appears that insect declines are substantially greater than those observed in birds or plants over the same time periods and this could trigger wide-ranging cascading effects within several of the world’s ecosystems.

The researchers are calling for a complete rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.

So what can we do as active participants in the current agricultural food chain? The key is to support agricultural practices that don’t require pesticide use and provide natural habitat for biodiverse species.  Organically certified farms meet both these criteria as the use of synthetic herbicides, pesticides and fertilisers is expressly forbidden.  In addition the organic standard requires that the farmer has at least 5% of their land set aside for natural, biodiverse habitat.

At Manna Hill Estate we have over 20% of the property dedicated to natural ecosystems.  In addition we have numerous shelter belts and mixed forestry coups that provide significant habitat for indigenous flora including more than 70 bird species that have been seen on the property.

 

Notes: 1) Worldwide decline of the entomofauna: A review of its drivers. Francisco Sánchez-Bayo, School of Life & Environmental Sciences, Sydney Institute of Agriculture, The University of Sydney, Eveleigh, NSW 2015, Australia, Kris A.G. Wyckhuys, School of Biological Sciences, University of Queensland, Brisbane, Australia; Chrysalis, Hanoi, Viet Nam; Institute of Plant Protection, China Academy of Agricultural Sciences, Beijing, China

 

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