Researchers have estimated the total economic value of global ecosystem goods and services showing that a significant portion of humanity's economic well being is unaccounted for in conventional GNP accounting (Constanza et al., 1997). To demonstrate this point, authors have conventionally used highly aggregated landscape units for analysis (e.g., biomes), and average, not marginal values, of each ecosystem good or service are estimated for each unit using value transfer methodologies (Wilson et al., 2004). For example, Patterson and Cole (1999a, b) replicated the Constanza et al., (1997) approach by estimating economic values for Waikato and New Zealand ecosystem goods and services associated with standard land cover classes including horticulture, agriculture and cropping. As a result, Patterson and Cole (1999b) argue that only five ecosystem services associated with cropping have non-zero value. One of the reasons for this low number of non-zero values assorted with arable lands is that the original economic studies used by Patterson and Cole, are heavily weighted towards natural and undisturbed ecosystems rather than disturbed systems like agricultural or urban landscapes. To address this issue, more recently researchers have noted that many landscapes are actively modified by humans who seek to realise economic gain and this topic is thus an important one because in the 21st century, many of our homes, workplaces and recreational spaces are embedded within, or adjacent to, landscape mosaics that are to a greater or lesser degree affected by the conscious efforts of people to harness goods and services provided by ecological systems (Palmer et al., 2004). An engineered or designed ecosystem is one that has been extensively modified by humans to explicitly provide a set of ecosystem goods and services including more fresh water, trees, and food products and fewer floods and pollutants. These modified landscapes provide a range of ecosystem goods and services, particularly food production as farmers seek to maximize commercial gain from land use. The current paper examines issues in valuation of ecosystem goods and services derived from land used for arable farming in New Zealand and proposes ways to provide more detailed estimates of the flow and value of the flow of ecosystem services provided.
