If wildlife are thriving, then it follows that their homes must be in good shape. One way to track progress towards healthy wetlands is to look at wildlife that depend on wetlands. The first group is wetland breeding birds, or birds that must have wetland habitat for nesting and raising their young.
What is the Current Status?
In SOGL 2017, the status of the wetland breeding bird Index of Ecological Condition (IEC) was assessed as 'Fair' to 'Good' for all lakes except Lake Erie, and the trend from 2011-2014 was 'Unchanging' or 'Improving' for all lakes except Lake Erie. Lake Erie was rated as 'Poor' and 'Deteriorating'.
How do birds relate to ecosystem health?
- Birds that breed in wetlands are sensitive to many aspects of their ecosystem, such as the available cover in their habitat, pollution runoff, and subsidized predators such as raccoons and house cats that are associated with nearby human development . The presence or absence of sensitive bird species can be a useful gauge of wetland health.
- Based on studies of how different species of birds respond to the condition of their habitat, ecologists calculated a number that correlates the general condition of the habitat with the likelihood of observing 52 wetland breeding bird species.
- This number is called the 'index of ecological condition' or IEC. The average IEC value, divided into categories of 'Good', 'Fair' or 'Poor', represents the relative condition of all the wetlands sampled around each Great Lake (Figure 1).
What is our objective?
Objective 1: Maintain or restore Great Lakes coastal wetlands to improve ecological conditions for wetland breeding bird populations in each Great Lake by 2030 (as calculated and reported in the State of the Great Lakes (SOGL) reports). Specific objectives by lake: All Lakes: Show an 'improving' trend. Lake Superior: Maintain 'Good' status. Lake Huron: Maintain 'Good' status. Lake Michigan: Achieve a 'Good' status. Lake Ontario: Achieve a 'Good' status. Lake Erie: Achieve a 'Fair' status.
Metric : Average wetland breeding bird Index of Ecological Condition (IEC) as reported in SOGL 2017.
Partners on this project include the Great Lakes Coastal Wetland Monitoring Program, Birds Canada/Oiseaux Canada, and the Great Lakes Environmental Indicator Project. All provided data published in the 2017 State of the Great Lakes (SOGL) Report. This included data from both Canada and the U.S., and combined the results of three extensive long-term bird surveys into one analysis.
Objective 1 addresses our goal because...
Wetland breeding birds are an important indicator of a healthy community of native plants, fish, insects, and other species in coastal wetlands. Objective 1 tracks the wetland breeding bird Index of Ecological Condition (IEC), which quantifies the relationship between wetland ecosystem health and an assemblage of wetland breeding birds.
Further Details on This Goal
How we picked the goal
- The Assembly chose Goal 1 to align with shared commitments outlined in the Great Lakes Water Quality Agreement (GLWQA) between Canada and the U.S. and the Great Lakes Restoration Initiative (GLRI) Action Plan III (U.S. only).
- For example, in the GLWQA, key commitments of the U.S. and Canada include "Facilitate binational collaborative actions to reduce the loss of native species and habitat, recover populations of native species at risk, and restore degraded habitat" and "Increase awareness of native species and habitat and the methods to protect, conserve, maintain, restore and enhance their resilience". Also in the GLWQA, Objective 5 and Annex 7 call for supporting resilient populations of native species and their habitats.
- In the GLRI Action Plan III:Objective 4.2 calls for increasing the resiliency of species through a comprehensive approach, and commits to supporting populations of both federally threatened and endangered species as well as Great Lakes native species.
Why we picked this metric
This metric was chosen with careful consideration. Ecologists have long used indexes related to many organisms, such as wetland plant species, amphibians, invertebrates, and birds, in order to gauge the relative condition of an ecosystem such as a wetland. For example, wetland breeding birds are included as indicators in the Great Lakes Biodiversity Conservation Strategies and the Lakewide Action and Management Plans for the Great Lakes.
For our first metric, wetland breeding birds provided a good starting point. They depend on many of the underlying components of coastal wetlands, they are popular with the public, and they are visible indicators of the quality of their habitat.
Using a quantitative measure like the Index of Ecological Condition (IEC) provided an objective way to illustrate the condition of coastal wetlands as reflected in wetland breeding bird populations.
Methods for calculating metric status
The Index of Ecological Condition (IEC) is an objective biotic indicator introduced by Howe et al (2007) and improved by Gnass Giese et al (2015). An IEC establishes a connection between environmental stressors and biotic variables by calculating an index that includes the following:
- 'Reference' gradients of environmental condition – for example, in the SOGL 2017 report, these conditions included agricultural intensity, non-agricultural landscape development, and wetland area.
- Sensitivity of species to environmental stress (a biotic response (BR) function). In the SOGL 2017 report, data from the Great Lakes Coastal Wetlands Monitoring Program were used to build these functions.
- Establish a specific assemblage of species to include. In SOGL 2017, 'wetland breeding birds' were defined as those that are at least partly associated with open wetlands during the breeding season. 52 species were used (Table 1 in SOGL 2017).
A detailed description of IEC methodology is available at http://www.uwgb.edu/BIODIVERSITY/forest-index/iec.asp.
To categorize the Status of wetland condition based on the IEC, definitions of Good, Fair, and Poor were calculated based on IECs from all years and all wetlands (n = 4,938). The 66th percentile and above of scores were assigned to the 'Good' category. The middle third were assigned to the 'Fair' category, and scores less than the 33rd percentile were assigned to the 'Poor' category, as follows:
- Good: IEC > 4.2
- Fair: 3.1 ≤ IEC≤ 4.2
- Poor: IEC < 3.1
Trends were assigned based on statistically significant changes (geometric mean rates of change) during the period from 2011-2014. Trends were defined as follows:
- Improving: increase in IEC from 2011-2014
- Unchanging: no significant change in IEC from 2011-2014
- Deteriorating: decrease in IEC from 2011-2014
Howe, R. W., R. R. Regal, J. Hanowski, G. J. Niemi, N. P. Danz, and C. R. Smith. 2007. An index of ecological condition based on bird assemblages in Great Lakes coastal wetlands. Journal of Great Lakes Research 33:93-105.
Gnass Geise, E.E., R. W. Howe, A. T. Wolf, N. A. Miller, and N. G Walton. 2015. Sensitivity of breeding birds to the 'human footprint' in western Great Lakes forest landscapes. Ecosphere 6(6):90. http://dx.doi.org/10.1890/ES14-00414.1
Summary of the data
In 2014, the mean IEC for each lake showed that Lake Erie was the only one in Poor condition, as measured using this metric (Figure 1). The mean IEC for the other lakes ranged from Fair to Good in 2014.
Based on this metric, Lake Michigan coastal wetlands were rated as 'Fair' and 'Unchanging', indicating a slightly lower mean IEC than Superior and Huron. The metric for Lake Ontario also fell in the 'Fair' range, but notably, it was the only lake basin where the trend was 'Improving'. Lakes Superior and Huron were rated as 'Good' and 'Unchanging'. The trend in IEC from 2011-2014 was Deteriorating only for Lake Erie.
To achieve Objective 1, Lake Erie would need to improve from 'Poor' and 'Deteriorating' to at least 'Fair'. Lake Ontario would need to improve to 'Good'. Lake Michigan would need to improve to 'Good'. Lakes Superior and Huron would need to start to trend to 'Improving'.
Additional Information provided in the SOGL 2017 report
In addition to publishing the average IEC values for 2014, the 2017 SOGL report provided the range of IEC values that were found from 1995-2014. This range indicates that the IEC can vary considerably when measured over several years. However, the mean IEC in 2014 is within the minimum and maximum range for each lake. Interestingly, Lake Erie was close to the low end of its range in 2014, which coincides with the finding that its IEC was Deteriorating between 2011 and 2014. Lakes Ontario, Michigan and Huron were towards the higher end of their range in 2014, consistent with their overall trends. Lake Superior appears the most variable, based on its large range of values from 1995-2014. This variability could be due to several factors.
Lake Mean IEC 2014 Range 1995-2014
- Erie 3.0 2.8 - 4.1
- Ontario 3.8 3.1 - 3.9
- Michigan 3.9 2.8 - 4.3
- Huron 4.6 3.8 - 5.0
- Superior 4.7 1.8 - 5.3
Caveats and Challenges
- The overall Fair and Unchanging status for the entire basin may be partially due to differences in sampling coverage; previous reports have relied on the mostly southern Great Lakes Marsh Monitoring Program dataset.
- Different study designs. The Great Lakes Marsh Monitoring Program allows volunteers to select sample points, but the Great Lakes Enviornmental Indicator Project and the Great Lakes Coastal Wetland Monitoring Program use stratified random sampling, although all used similar wetland types.
- The BR (biotic response function) only included data from the Great Lakes Coastal Wetland Monitoring Program. If this could be expanded to include all available bird data, the resolution of the Index of Ecological Condition (IEC) could be stronger.
- Also, the IEC factored in only 3 stressors, and left out other factors such as dominance of invasive plant species, or water levels.
Information on the data sources
All data are as reported in the State of the Great Lakes report – 2017
In the SOGL report, data were used from: