Monitoring for Policy-Relevant Regional Trends over Time

Abstract

The term trend describes the continuing directional change in the value of an indicator, generally upward or generally downward. Many policy questions concern trend across a number of sites, such as lakes in a region, rather than trend at a single site. Power to detect regional trend seldom is discussed, and monitoring designs suitable for detecting such trends rarely are explored. Components of variance and temporal sampling designs play central roles in characterizing trend detection. We present relative numerical values of important components of variance, developed from the Surface Waters component of U.S. EPA's Environmental Monitoring and Assessment Program (EMAP) field data, and use them as a basis for further assumptions of values. We discuss power curves in general and present them in relation to temporal designs, years of field observation, components of variance, and the level of trend detected. Revisit designs give adequate power for moderate trend in 10-15 yr, even when revisits are less frequent than annually.

Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three‐Gorges Reservoir, China

“…High temporal coherence indicated that data gathering in few sites is available for understanding regional lake trends, while low spatial synchrony indicated that results obtained in a single site cannot be extrapolated to the entire regional lakes (URQUHART et al, 1998;LANSAC-TÔHA et al, 2008). Low temporal coherence for chlorophyll a detected by the study showed that trend for phytoplankton observed in a single site can not be extrapolated to the entire Xiangxi Bay.…”

“…Some researchers pointed out that short term time series may preclude the detection of synchronous dynamics and trends (URQUHART et al, 1998;PATOINE and LEAVITT, 2006). Most studies on temporal coherence of limnological variables were based on correlation analysis of long time series over many years at low sampling frequencies (RUSAK et al, 1999;BAINES et al, 2000;CHRZANOWSKI and GROVER, 2005;PATOINE and LEAVITT, 2006).…”

“…In addition to the explanation of the factor controlling phytoplankton dynamics, the present study has one implication for the design of monitoring programs in a reservoir-bay. As pointed out by (URQUHART et al, 1998;LANSAC-TÔHA et al, 2008), a set of sampling sites should be observed in the program for monitoring a single system (i.e., a reservoir of approximately 65 km 2 ) with high spatial heterogeneity. Similarly, a set of sampling sites should also be required for a successful observation on the dynamics of a single reservoir-bay.…”

Cost-effective Sampling Design Applied to Large-scale Monitoring of Boreal Birds

“…Ecological monitoring, the repeated measurement of biotic response to disturbance (Hinds 1984), provides this feedback, thereby facilitating adaptive management (Halbert 1993) and the establishment of conservation and research priorities (Burbidge 1991, Stork andSamways 1995). Large-scale monitoring, where detection of long-term trends over broad spatial scales is the goal, improves our ability to distinguish human impacts from natural changes (Spellerberg 1991) and allows inference at scales relevant to policy (Urquhart et al 1998).…”

Optimising survey effort to monitor environmental variables: A case study using New Zealand kiwifruit orchards

“…This is often technically and logistically challenging, especially when treatment impacts vary from site to site (Raudenbush and Liu, 2000) and/or resources are limited (Lindenmayer and Likens, 2010;Magurran et al, 2010). Careful planning and executing of sophisticated analyses of monitoring data are recommended for identifying: cost-effective and robust designs (Field et al, 2007;Geijzendorffer et al, 2015;Johnson et al, 2015); monitoring efforts that have no realistic chance of detecting relevant changes, and options for improving them (Collen and Nicholson, 2014;Field et al, 2007;Legg and Nagy, 2006); and trade-offs between spatial and temporal replication (Rhodes and Jonz en, 2011;Urquhart et al, 1998).…”