Is what you see what you get? Visual vs. measured assessments of vegetation condition

Abstract

Summary1. An important step in the conservation of biodiversity is to identify what exists, its quantity and its quality (i.e. condition). This can be a daunting task at the landscape-scale, so vegetation communities are often used as surrogates for biodiversity. Satellite imagery has improved our ability to rapidly measure vegetation parameters but the need for calibration still requires rapid and cost-effective on-ground condition assessment. Some management agencies address this need by using visual condition assessments, with unknown consequences for the different purposes of condition data. It is therefore vital to examine the comparability of visual and systematic condition assessment methods to guide their use in conservation decision making. 2. We compared visual assessments of vegetation condition with more systematic and higher resolution on-ground assessments, using a method where both assessments were made for the same quadrats. We determined both the condition parameters observers respond to when making visual assessments of condition, and the consequences of any differences for the application of these data. 3. We found that visual assessment of vegetation condition broadly represented measured assessments of the same vegetation, but that observers simplify their assessments by responding to only some of the measured condition parameters. No consistent trends were found in the parameters observers responded to across the different vegetation types sampled. 4. Synthesis and applications. We conclude that visual estimates of vegetation condition are only of sufficient resolution to replace more expensive, high-resolution assessments at a landscape-scale, when condition results are combined over multiple areas and vegetation types. Visual assessment methods potentially can provide an efficient measure of overall condition for conservation management agencies where practitioners can make assessments of condition in the course of their daily management activities -an important step forward. At smaller scales, idiosyncratic effects render visual estimates highly variable when compared with systematic condition assessments. This variability, especially among vegetation types, suggests that more systematic assessments are necessary when management decisions require higher-resolution estimates of changes in individual condition parameters, such as when measuring the success of individual management actions. These findings provide a valuable guide for selecting the most appropriate approach for the different objectives of condition assessments for biodiversity conservation.

Rapid Assessment of Roadsides as Potential Habitat for Monarchs and Other Pollinators

“…In general, averaging parameter estimates for multiple Rapid Assessments yielded more consistent results than any single Rapid Assessment from sites, suggesting that combining multiple Rapid Assessments to characterize areas is preferred over single samples. This is similar to a comparison of rapid qualitative score to quantitative scores of vegetative condition, where there was broad association in the scores across many sites, but rapid assessments were not reliable at the level of a specific site (Cook et al, 2010). Furthermore, this underscores our recommendations that managers sample multiple sites.…”

How accurate is the local ecological knowledge of protected area practitioners?

“…Inaccurate assessments of condition could lead to poor management decisions attributable to the premature cessation of vital management programs or by misdirecting management resources through a failure to recognize when programs are not needed. However, where subjective estimates of vegetation condition represent a good surrogate for empirical data, they provide a fast, cheap alternative to resource-intensive sampling techniques (Cook et al 2010b). We found that estimates made by practitioners tended to be pessimistic relative to the empirical scientific estimates (Fig.…”

“…In contrast to the costs of collecting empirical estimates of vegetation condition, LEK has the advantage of being relatively cheap and readily available. However, vegetation condition can be a complex concept (Keith and Gorrod 2006) that is challenging to objectively assess and to judge visually (Cook et al 2010b). Biodiversity conservation is the primary goal of protected area management; therefore, we adopt the definition of vegetation condition used by Keith and Gorrod (2006) as it relates to biodiversity: the capacity of vegetation to sustain local populations of plants and animals, their genetic diversity, and ecological interactions.…”

Same Viewpoint Different Perspectives—A Comparison of Expert Ratings with a TLS Derived Forest Stand Structural Complexity Index

“…Forest structure has multiple aspects and a broad variety of indicators exist to describe these for retention purposes. While forest managers mostly have to rely on their subjective visual impression when they decide which trees or group of trees will be retained [10], different criteria have been evaluated to make these decisions more objective. First attempts to describe quantitative structural complexity used diversities of tree diameters at breast height (DBH), tree size differences, or spatial patterns of tree locations [11][12][13][14][15].…”