Biodiversity is defined by Wikipedia as ‘the degree of variation of life forms within a given species, ecosystem, biome, or planet’. These diverse life forms combine to form what we term ‘ecosystems’ which provide oxygen, clean air and water, and healthy soil. They help regulate the climate, promoting stability in the environment. It is now considered that biodiversity is under threat due to climate change as well as loss of habitat through industrialisation and agricultural activities. Well, last week I came across a report in The Australian that set off more alarm bells in my head. It seems that conventional farming is not as ‘safe’ for our ecosystem as pesticide regulators would have us believe.
A new kind of study
The article referred to a publication in the major scientific journal, Proceedings of the National Academy of Sciences (1), which provides evidence that agricultural insecticides are more harmful to biodiversity than was originally thought. A collaborative study between scientists in Australia and Germany showed that high levels of pesticides in rivers and streams were associated with a reduction by up to 42% in biodiversity of invertebrates (including dragonflies, stoneflies, caddisflies and mayflies) in the European sites, and by up to 27% at the sites in Victoria, compared to waterways with relatively low pesticide levels. In areas with high levels of pesticides, whole families of species were missing.
The extensive sampling done in this study was unique – the first of its kind in the world - allowing the statement to be made that biodiversity was affected by insecticides on a regional scale. Of particular concern, biodiversity loss was seen when pesticides were used at levels considered ‘protective’ according to European standards, that is, at levels considered safe in the environment.
A hidden cause of biodiversity loss?
At the Convention on Biological Diversity in 2002 (see their website here ), world leaders agreed to aim to reduce the rate of loss of biodiversity by 2010. It is stated in ‘Global Biodiversity Outlook 3’ published in 2010, ‘..this target has not been met. Moreover, ...the principle pressures leading to biodiversity loss are not just constant but are, in some cases, intensifying.’ Continuing degradation and loss of habitat are considered by most to be the major cause. The study mentioned above suggests that pesticides could well be an additional major contributor to biodiversity loss, even when they are used at levels considered safe.
Neonicotinoid pesticides – the tip of the iceberg?
Of particular concern is the class of insecticides, the neonicotinoids, which first came into widespread use in the 1990s (for review see (2)). They currently comprise around 25% of all insecticide use world-wide, and are most commonly used as a seed dressing. They are attractive to farmers since once a treated seed is planted, no further insecticide treatment need be used for a few months, as the insecticide diffuses through all parts of the growing plant. The bad news is that at sowing, at least 80% of the insecticide is not bound to seed – a small proportion is released as dust, while the remainder goes into the soil. Being water-soluble, it leaches easily out of soil into streams and rivers. Insecticide that does remain in the soil may remain active for up to 3 years, accumulating and impacting on soil invertebrates, and being incorporated into plants, both wild and farmed, for many months afterwards.
Of particular concern has been the possible impact of these insecticides on honey bees, which have been in severe decline in recent years in many parts of the world. See our blog discussing this: (Bee products and skin care)
Seed-treated plants accumulate small amounts of the neonicotinoid insecticides in their pollen and nectar, to which foraging bees are exposed. Although the dose they would be expected to receive from seed-treated plants is not considered lethal, doses they are likely to ingest have been shown to affect learning, foraging and homing ability, and at least in bumblebees, severely reduce reproductive ability, where an 85% drop in queen production was recorded. These effects on bees are worrying enough, but the impact on other insects has never been examined.
Europeans ban neonicotinoids
In April this year, the European Commission decided to impose a 2 year ban on 3 neonicotinoid insecticides, because of the suspicion that they may be contributing to the massive decline in bee populations. These 3 insecticides will be banned from December 1, 2013, on flowering crops such as corn, canola, sunflower and cotton, but will be permitted on winter cereals and crops not attractive to bees.
Notably, the USA has decided to impose no restrictions on these pesticides, whilst Australia is considering its position (3).
A new look at conventional agriculture
We do not know which insecticides contributed to the loss of biodiversity in the newly released study. However, it is clear that the current system of determining the ‘safe’ level of use of insecticides is not working. As stated by the authors of the study, ‘Thus, the current risk assessment standards and/or their implementation in agricultural practice are not protective for regional biodiversity of the stream invertebrates.’ In other words – the levels of pesticide use currently considered safe to our wildlife, are not. The authors suggest that this is because toxicity testing of pesticides is normally carried out in a laboratory, or simulated river conditions, and its effects measured on a small scale.
Clearly, the ecological impact of applying insecticides in the field should likewise be studied at the same scale. This is not done before an insecticide is released onto the market and our ecosystem, nor is it done after its release to determine whether the real impact matches the prediction. Nor are studies carried out to determine whether sub-lethal doses of insecticides have behavioural effects on insects which could potentially reduce their capacity to thrive.
Surely this has to be another wake-up call to put more of our education and research dollar into incorporating organic farming methods into conventional agriculture. Although the traditional response to this type of suggestion is that organic farming simply will not feed the world, there is a groundswell of evidence that this may no longer be the case (See links to articles on this topic below).
Either way, because of the continued pressures on all ecosystems from climate change, it now seems clear that ‘business as usual’ style agriculture is going to push biodiversity further on its downward spiral. This means severe consequences for humans and the rest of life on the planet – further loss of biodiversity will reduce the resilience of our ecosystem. We have the means to check it. Let’s rethink pesticides and put our resources into working on alternatives. Or, if that’s too hard, let’s work out ways to at least be smarter in how we use them.
References:
(1) ‘Pesticides reduce regional biodiversity of stream invertebrates’ Mikhail A. Beketova, Ben J. Keffordb, Ralf B. Schäferc, and Matthias Liessa. Proceedings of the National Academy of Science 2013
(2) ‘An overview of the environmental risks posed by neonicotinoid insecticides’ Dave Goulson, Journal of Applied Ecology. 2013
(3) Neonicotinoids and honey bee health in Australia Release by the Australian Pesticides and Veterinary Medicines Authority.
Read more about the organic vs conventional farming debate:
Can organic farming feed us all?
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