A proposed framework for determining the environmental impact of replacing agricultural grassland with Miscanthus in Ireland

Abstract

Energy crops offer an opportunity to substantially increase bioenergy resources which can replace rapidly depleting fossil fuel reserves and mitigate the effect of climate change. Energy crops are typically established within traditional agricultural systems such as tillage land or grassland. Associated land use conversion has environmental implications. The aim of this paper is to propose a framework to examine how such environmental implications can be assessed, based on (a) a Strategic Environmental Assessment (SEA) approach which considers potential impacts at different stages of a plan across a wide range of environmental receptors and (b) a literature review. The example we used was that of Miscanthus replacing grassland farming. This scenario is particularly relevant to Ireland, where over 90% of the agricultural land is permanent pasture, but is also applicable to grassland conversion throughout Europe and the United States. Two consecutive phases of land-use change were identified for assessment, each with a distinct set of environmental impacts. The first was a transition phase, lasting from initial livestock clearance and grassland ploughing until the Miscanthus crop became established (2-3 years). The second phase was the mature crop phase, lasting up to 25 years. Miscanthus cultivation was more likely to impact negatively on the environment during the transition phase than the mature phase, primarily due to abrupt disturbance and the time required for a new equilibrium to establish. However, a literature review of the impact on the environmental receptors revealed that replacing Irish agricultural grassland with Miscanthus had the potential to improve biodiversity, water, air and soil quality, and climatic factors once the crop became established and reached maturity. In order to confirm these findings an appropriate monitoring programme involving objectives and indicators associated with each environmental receptor would need to be developed.

Miscanthus production and processing in Ireland: An analysis of energy requirements and environmental impacts

“…The establishment of Miscanthus on tillage soils results in benefits in terms of improved nutrient and moisture retention, reduced wind and water erosion [24,25], and improved drainage [18]. These benefits are also observed, albeit to a lesser extent, when established on grassland sites once the crop reaches maturity [18]. Soil erosion is lower than on annual crops as cultivation and establishment is only repeated once over the lifetime of the crop [26,27].…”

“…During establishment of Miscanthus, high rates of mineralisation following ploughing can result in significant losses in organic carbon and nitrogen [18,[29][30][31]. However, once established, the perennial nature of Miscanthus allows the accumulation of soil organic carbon (SOC) in differing quantities depending on soil type and previous land use [28,32,33].…”

“…When replacing grassland with Miscanthus, an overall increase in biodiversity results in a greater number of species being present [18]. Similarly, biodiversity in Miscanthus is also higher than it is in conventional annual crops [22].…”

“…As such, Miscanthus has high net energy content when compared to other energy crops [17]. In addition, Miscanthus has high water and nutrient use efficiencies, making it a low input crop [18][19][20].…”

Miscanthus: a case study for the utilization of natural genetic variation

“…There is a need to generate new broadly adapted genotypes suitable for a range of environments including both agricultural and marginal lands Chou, 2009;Jørgensen, 2011;Qin et al, 2011;Jing et al, 2012;Nijsen et al, 2012). There is a movement towards developing crops suited for marginal land so that fertile land is not taken away from food production Donnelly et al, 2011;Gopalakrishnan et al, 2013). For example, the EU FP7 project GrassMargins aims to develop genotypes suitable for growth on European marginal land (http://www.grassmargins.com).…”