The concept of threshold and its potential application to landscape planning

Abstract

The concept of threshold can potentially be applied to conservation planning of species, habitats, and ecosystems. It also has significance in managing socialecological systems for resilience. However, our understanding and use of threshold has been scattered among various disciplines, and the link to conservation planning and social-ecological system management has not been strongly established. The review of the use of threshold in various disciplines reveals that the term is used in a similar manner in both natural and social sciences: a threshold is a point or a zone on an independent variable, and if it is crossed, a sudden, large change in the state of a dependent variable occurs. Even a small change in the independent variable brings this drastic change; nonlinear relationship characterizes the threshold response. Thresholds also separate alternative regimes in a social-ecological system. The discussion of the application of threshold concept to watershed planning concludes that although using one threshold value of impervious surfaces in a watershed to regulate new developments and retrofit old ones is a cost-effective method, a more integrated approach is needed. The use of habitat amount threshold to conserve species promotes proactive planning that would prioritize areas for protection before the threshold is reached and would restore habitat based on the threshold target. However, species-specific data to decide on the threshold is often lacking, and the identification of thresholds is not straightforward. Nonetheless, the concept of threshold is appealing for proactive planning and significant in managing social-ecological systems for resilience.

The proportion of impervious surfaces at the landscape scale structures wild bee assemblages in a densely populated region

“…Our results indicate a correlation between the proportion of impervious surfaces within a 500 m radius and the structure of bee assemblages in the Île‐de‐France region. In this context, determining a precise threshold for the proportion of impervious surfaces above which permanent changes occur in bee assemblages could greatly improve conservation measures for pollinating insects and plants within cities and should have implications for future urban landscape planning (Kato and Ahern ). As the world continues to change rapidly and becomes increasingly urbanized, new conservation policies are needed to preserve the ability of anthropized areas to provide habitats for pollinators.…”

Assessing Sustainability of Agricultural Systems: Balancing Context Specificity and Generality

“…"Once-size-fits-all" benchmarking approaches tend to disregard the local conditions and diversity of environmental, economic and cultural drivers that affect individual production performance (von Wirén-Lehr, 2001;Nader et al, 2008;Huggins, 2008[cited in van Zeijl-Rozema et al, 2011; Kato et al, 2011). Decoupling the benchmarking process from these drivers presents the risk of setting non-practicable targets, discouraging farmers' adoption of the information for learning, and undermining trust in the whole sustainability exercise.…”

The Impacts of Impervious Surface on Water Quality in the Urban Agglomerations of Middle and Lower Reaches of the Yangtze River Economic Belt From Remotely Sensed Data

“…Several studies have proposed a non-linear relationship between PISA and water quality, and have found that water quality degradation was associated with higher PISA values [5], [24]. In addition, it has been concluded that the threshold PISA values at which point water quality degradation begins are a critical factor in this relationship analysis [25], where these thresholds may depend on regional conditions and their different stages of urban and industrial development [16]. For example, Kim et al (2016) found that PISA threshold values for several water quality indicators (including biological oxygen demand (BOD), permanganate index (CODMn), total organic carbon (TOC), and total phosphorus (TP)) was 9.80% for the Han River Basin of South Korea [24].…”