By Jacqui Meyer
Greta Thunberg’s climate change challenge to UN leaders on 23 September 2019 got me to thinking:
As an industry we tend to focus on the compartment or plantation level impacts of pesticide use, rather than on the global impact. The forestry value-chain, as we know, can be both a source and a sink for carbon, how much of this can be attributed to pesticide use?
So, I decided to do a bit of homework.
Google ‘pesticide use’ and ‘climate change’ and you soon realize this is a controversial and polarizing issue. Both ends of the argument churn out huge amounts of literature to “support their cause”.
However, a few dedicated hours of wading and sifting produced a number of meaningful articles and valid arguments that can be applied to forestry. Most of the research focuses on annual (food) crops.
There is a convincing argument for an increase in crop pest prevalence as a result of warmer winters/prolonged summers associated with climate change that will provide extended feeding opportunities. Pesticides will inevitably play a greater role in the future when it comes to controlling these predicted pest outbreaks and to ensure that healthy crops and productive yields are maintained.
Yet there are those who argue that by using pesticides to counteract the proposed symptoms of climate change, we are only adding to the underlying issue. Their argument is that pesticide manufacture, distribution, application, and at times, the pesticide’s mode of action only exacerbates the issue of climate change.
So, is this the case for forestry?
Agriculture in general is one of the most significant contributors to carbon emissions, according to CropLife International. Although, a large proportion of the quoted emissions result from livestock production and changes in land-use, which for the most part is no longer an issue associated with South African forestry industry.
Crop production, however, contributes about 14% of the emissions and this is where agriculture and our industry can look at ways of adapting to reduce emissions. Practices that increase soil carbon sequestration, protect carbon sinks and decrease the relative intensity of carbon emissions can positively reduce our sector’s contribution to climate change.
When it comes to reducing the intensity of carbon emissions, we need to take a long look at the production cycle of our crop, as many factors contribute to its overall footprint. Crop protection products are often cited as an area where a major reduction in emission levels can be made, but how realistic is this?
Croplife International reports:
“Crop protection products, pesticides to you and me, contribute only a small percentage – < 1-4% – to the overall carbon footprint of a cultivated crop.”
This is supported by the work of Audsley, et.al. (2009) who, based on the weighted average pesticide energy input required by a range of arable crops, reports that the pesticide energy input of 1364 MJ/ha corresponds to a weighted average greenhouse gas emissions of 94 kg carbon dioxide equivalent per hectare of arable crop.
What we need to bear in mind is that this relates to annual crops not plantation forestry. Figures for a one hectare Eucalyptus compartment can be extrapolated from this, based on the notion that pesticide usage is normally confined to the first year of a 10-year rotation. Thus the 94 kg carbon dioxide equivalent is then shared over 10 years equating to a carbon dioxide equivalent of 9.4kg per year.
So, what does this mean?
While 9.4kg does not sound like a huge amount of carbon dioxide, when considered at the landscape level – 12,000 tonnes – it suddenly sounds like a far greater contribution. So, should we stop all pesticide use now in order to reduce our carbon footprint?
First, we need to look at this figure in context, according to the Green Vehicle Guide:
“A typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year, although this number can vary based on a vehicle’s fuel, fuel economy, and the number of miles driven per year.”
After some scary calculations to work out the carbon equivalence, this equates to approximately 2.44 metric tons of carbon dioxide emissions per vehicle per year. To place forestry’s pesticide use in context, it is equivalent to the emissions produced by just under 5,000 cars – the number of units sold in South Africa in just over three days.
Suddenly the impact of the sector’s pesticide use doesn’t seem like such a pressing issue, when considering climate change on a global level. If, as a sector, we do wish to reduce our carbon footprint and contribute to reducing the threat of global climate change, we need to look at other aspects of the value chain.