Global lifestyles in developed nations continue to cause too many greenhouse gas emissions. Removing some of these emissions is one required remedy. Most of us already know one example of a natural remedy — trees.

Trees extract carbon dioxide from the atmosphere and store it for decades, even centuries, in their limbs and roots. So this option to reduce emissions is tantalisingly simple to implement. Just plant more trees!

Although that advice is appealing, responding to its apparent wisdom is not without difficulty as many questions subsequently arise such as: where should these trees be planted? How many need to be planted? Are there only environmental benefits from planting trees or are there also economic costs and benefits?

There may be no single answer to such questions, which is perhaps illustrative of why the social and political debate surrounding emissions management is at times fierce, even polarised.

The role of trees in agricultural regions

My research experience is in agriculture in Western Australia, so I will confine my comments to the role and value of trees in this State’s agricultural region in emissions management.

Professor Ross Kingwell teaches in the UWA School of Agriculture and Environment

Firstly, emissions from agriculture in Western Australia have been mostly stable since 2012 at just under 10,000Gg carbon dioxide annually. These emissions form 10 per cent of the State’s emissions but are dwarfed by the energy sector that generates 83 per cent of the State’s emissions. Planting trees in agricultural regions is one option for farmers to offset or abate their own industry’s emissions.

Secondly, what is often underappreciated is that many farmers have already committed parts of their farmland to revegetation and agroforestry. These activities biologically fix or sequester carbon dioxide, thereby helping reduce net emissions. The magnitude of this sequestration is such that, for example, in 2020 nearly all (97.5 per cent) emissions from agricultural activities in Western Australia were balanced by carbon sequestration activities on land managed or owned by agricultural businesses. So, carbon neutrality for the State’s agricultural sector appears within reach.

Whether planting more trees is the most cost-effective way of finally achieving carbon neutrality for agriculture or any other sector is an interesting question. In my view there are better, longer-lasting technological solutions that, at source, prevent or reduce emissions.

Planting trees to be permanent stores of sequestered carbon overlooks their exposure to bushfires that can undo decades of sequestration.

Thirdly, the emerging challenge for agriculture in this State likely comes not from farmers switching farmland into tree plantations to deliver carbon neutrality for agriculture. Rather, the challenge likely comes from sectors outside agriculture that seek to buy and convert farmland into forestry plantations to offset their own sectoral emissions. Such changes in land use have many economic and social ramifications.

Planting trees is far less labour-intensive than ongoing agricultural activity and generates far fewer value-adding or industry multiplier opportunities. Regional economies are far more likely to be less economically and socially vibrant when large swathes of farmland are converted into permanent forests. Also, switching land away from food and fibre production reduces the State’s potential agricultural export income.

Lastly, the harsh reality for tree plantations is that trees eventually mature and no longer continue to store inexorably increasing amounts of carbon, making tree planting a likely second-best option. Yes, trees, in the absence of bushfires, provide sequestration for a handful of decades, but the first-best option is to efficiently reduce emissions at source. That solution requires technological and policy innovation.

So, maybe more trees in agricultural regions for emissions abatement is actually not unambiguously preferable. That said, trees do perform other useful roles in providing shade, habitat, visual amenity, increased biodiversity and some tree species can be sources of renewable fuel.

By Professor Ross Kingwell

Professor Ross Kingwell teaches in the UWA School of Agriculture and Environment. He is also chief economist with the Australian Export Grains Innovation Centre and the Department of Primary Industries and Regional Development. His research focuses on grain supply chain analyses, strategic market opportunities for Australian grains, farming systems analysis, and agricultural emissions management.

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