Inter-observer variation in habitat survey data: investigating the consequences for professional practice

Abstract

Environmental assessments and land use planning require reliable information on the botanical composition and distribution of habitats. There have been numerous academic studies of inter-observer variation in species-inventory and habitat mapping, but studies addressing the prevalence of inter-observer variation and consequences of poor quality data in professional practice are lacking. This paper addresses these questions via a questionnaire survey of environmental professionals using the standard Phase 1 and National Vegetation Classification (NVC) survey methods in the United Kingdom. The survey revealed that misidentification of habitat types within survey reports was relatively common (approximating to 20% of all reports seen by respondents over the previous five years).Approximately 40% of respondents who had encountered erroneous reports stated that these had led to inaccurate initial site ecological assessments. Additional field surveys and discussions with surveyors were commonly used to resolve these issues, but for Phase 1 and NVC 26% and 34% of respondents respectively had encountered one or more cases where errors resulted in negative consequences for clients commissioning surveys (in terms of extra costs and project delays). Net loss of biodiversity arising from inaccurate reports was reported in at least one instance by 32% and 38% of respondents for Phase 1 and NVC surveys respectively -results that may contribute to the attrition of natural capital within the UK. The study highlights the need to extend studies of inter-observer variation to consider impacts on environmental assessments and decision-making in professional practice. The potential benefits of introducing an accreditation scheme (favoured by the majority of respondents to the questionnaire) are discussed.

The Implications of Field Worker Characteristics and Landscape Heterogeneity for Classification Correctness and the Completeness of Topographical Mapping

“…This means that some field workers are not successful in correctly mapping specific features. This agrees with studies that explored the accuracy of vegetation mapping, which found that individual skills affected the values of MCO error rates [34,35,56]. Moreover, our results indicated that in some landscapes, individual characteristics may have had a bigger effect on mapping quality than in other landscapes.…”

“…For example, in the built-up-diverse landscapes, the variation of error rates and overall error rates were lower than in closed-complex and open-simple landscapes, which suggests that built-up areas were easier to map than natural areas. In contrast, different vegetation communities that are similar in species composition and appearance can be easily confused in fieldwork in natural areas [35,56].…”

Point of view: error estimation in field assignment of land-cover types

“…Failure to take potential error in land-cover maps into account may have unfortunate consequences for practical management, such as giving priority to low-value sites while sites of higher conservation value are lost. In a survey among British environmental professionals (Cherrill 2016), about one third of the respondents reported experience with net loss of biodiversity due to errors in assignment of land-cover types. In many more cases, mistakes incurred additional costs for the respondents' firms or clients.…”

“…the process of drawing a multitude of non-overlapping unique land-cover polygons covering the entire extent of the intended map. Cherrill andMcClean (1995, 1999a) indicated that very different placement of boundaries in compared maps are likely due to differences in land-cover-type assignment rather than differences in the observers' perception of transitions between types. They applied buffers around polygon boundaries and compared only the 'core areas' of polygons to separate the effect of type assignment.…”

Consistency in land‐cover mapping: Influence of field workers, spatial scale and classification system

“…Appropriate management depends on correct assignment of sites to types (Cherrill & McClean, ) and consistent delineation of polygons (Hunter, ). Net loss of biodiversity may result from the use of land‐cover maps that fail to meet these demands for quality (Cherrill, ). One of the most important obstacles to consistency in field‐based land‐cover maps is among‐observer behavioral differences, i.e.…”