The "wonder crop": what impact does Miscanthus have on biodiversity?

Posted by Sara King BSc (Hons) MCIEEM on 22/07/2019

 

Climate change is pushing firms and governments to start to use alternative energy sources to cut and eventually eliminate the use of fossil fuels. Plant based biofuel crops are one of these alternatives, and they have been used for several years now. Miscanthus (or elephant grass) is sometimes referred to as the "wonder crop", as it is efficient, cheap to grow and profitable for farmers. The US in particular has committed $80m investment to bioenergy research and development, with the aim of expanding the bioenergy market. Miscanthus is fast growing, which helps with its efficiency as a biomass crop. It also grows densely, and to a height of 3 metres, which can shade out all other competing plant growth. This reduces potential food plants for wildlife, particularly invertebrates, in the centre of the field. Large areas of miscanthus, therefore, is unlikely to support high levels of biodiversity.  

 

 

That being said, however, the impact of this crop on biodiversity is relatively unknown. A new study conducted by Dr Alan Feest and Mike Williams, supported by Ecosulis, has undertaken an assessment of the impact miscanthus crops have on biodiversity using invertebrates as an indicator of biodiversity quality. The study was undertaken in Somerset, and collected data from a miscanthus field, as well as adjacent fields that supported mixed use arable and a grazed grassland field.

 

Biodiversity Assessment

Pitfall traps were set in all three fields to collect data on invertebrate use for just over two years. A total of 20 sample points were selected in a standardised way for each field, as 20 sample points have been found to record at least 80% of species in most cases. Invertebrates are great indicators of environmental change as well as biodiversity within a system. The work was undertaken between 2008 and 2011 by Mike Williams. A similar approach can be undertaken now which could utilise DNA barcoding to identify invertebrates, and encourage citizen science projects.

 

Biodiversity Quality Calculator

The Ecosulis Biodiversity Quality Calculator was used to compare Miscanthus, mixed arable and grazed grassland fields. It provides quantitative outputs, generating information related to specially selected biodiversity indices.

This approach allowed the biodiversity quality associated with different crops to be directly compared, and give us a full picture of the impact they each have on biodiversity. The results are summarised below.

 

  • Mixed arable field supporting barley had the highest biodiversity quality for ground beetles, including biomass and species rarity in Year 1
  • Linseed supports the highest biodiversity quality for ground beetles in Year 2. Miscanthus had the highest species rarity.
  • Arachnid populations were better in grazed grassland habitats (with higher species richness, biomass and abundance), compared to the Miscanthus crop

 

 

Miscanthus is poor for biodiversity quality compared to other crops

Overall, the study has shown that all the other crops provided higher biodiversity quality than miscanthus crops. Replacing mixed-arable land or grazed grassland fields with miscanthus will therefore have a negative affect on biodiversity.

There are obvious benefits to biofuel crops – they reduce fossil fuel use globally, therefore have a lower carbon footprint. However, consideration needs to be given to the impact this dense monoculture crop is having on our already declining biodiversity. This innovative study aims to provide quantitively robust information to inform the impact miscanthus has on biodiversity, and to assist with informing decisions.

We would like to see additional measures implemented to improve biodiversity within our farmed landscape, which could include: 

  • A variety of crops utilised to provide a mix of opportunities for wildlife 
  • Large field margins supporting plants and food sources for a variety of species
  • Mitigation areas to support invertebrates.

 

If this could be implemented for biofuel production, this could result in a reduction in carbon emissions as well as an increase in biodiversity within our countryside. It is important to ensure that we pursue more sustainable sources of fuel, however natural solutions are equally important to reduce the impact of climate change. Biodiversity is also key to crop and food production on site, and must be considered within biofuel strategies globally - we hope that this study is a first step to help inform future strategies and decisions. 

 

The full study can be found at: http://m.scirp.org/papers/93714