Indirect land use change (iLUC) refers to the unintended conversion of land elsewhere in response to a direct change in land use in a specific location. This phenomenon occurs when an Activity that converts land for a new purpose displaces the previous land use, which must then be relocated to another geographical area, potentially causing environmental impacts such as deforestation, loss of biodiversity, or carbon emissions from soil and vegetation changes.
The concept is particularly relevant in consequential Life Cycle Assessment, where the full chain of cause-and-effect relationships must be captured. Whilst direct land use change is straightforward to observe and measure at the site where an activity occurs, indirect land use change represents the displaced effects that ripple through interconnected agricultural and forestry systems globally.
A common example illustrates the mechanism clearly. When agricultural land is converted to grow crops for biofuel production, the food or feed crops previously grown on that land must still meet market demand. This displaced production often occurs through expansion of agricultural land elsewhere, frequently involving conversion of forests, grasslands, or peatlands. These indirect conversions can generate substantial greenhouse gas emissions and other environmental burdens that should be attributed to the original land use decision when using consequential system modelling approaches.
ISO 14040 and ISO 14044 do not explicitly define indirect land use change, but the standards' principles regarding system boundaries and completeness of inventory analysis provide the framework for including such effects. The challenge lies in determining appropriate system boundaries and identifying which market-mediated effects should be included in a Product system.
Quantifying indirect land use change impacts remains methodologically complex, involving economic modelling of land markets, agricultural production responses, and spatially explicit analysis of where displaced production is likely to occur. Different modelling approaches can yield significantly different results, making iLUC one of the more controversial aspects of life cycle impact assessment for land-based products.
