Cumulative Effects

The General Idea

Cumulative effects are the net changes to values in the environment and/or society that result from a land-use activity. We have identified large areas of the Dawson Region where we feel some development, and their negative effects, are acceptable. These are known as the Integrated Stewardship Areas - please see the Land Designation Sytem page for more information.

So in the ISAs, we can accept some negative effects, with more in the ISA IV ("Highest Development") than in the ISA III ("High Development") and so on. But what do we mean by "more"?

Indicators

We are interested in the cumulative effects on many values, such as caribou, cultural elements, wetlands, and more. However, it is difficult to measure any one of these, and impossible to track all of them. So we selected two disturbance indicators described below were chosen to keep consistent with other Yukon regional plans and because they indirectly relate to many regional values or issues like habitat amounts, habitat intactness, access and hunting pressure. Put more succinctly, monitoring the two indicators should indirectly monitor the effects on many of the values in the Region.

Surface Disturbance

Commonly referred to as "footprint", surface disturbance refers to the area of land physically disturbed by human activities. It is measured as the percentage of a given area (e.g., Land Management Unit) that is disturbed.
Surface disturbance can be determined using satellite imagery together with project proposals or reports. It can also be used with maps of values to determine other indicators such as disturbance to high valued caribou habitat.

Linear Density

Linear density is the total length of all human-created linear features (roads, seismic lines, trails) in a given area (represented as km of access per km² of area). Linear density can be used as an indicator of fragmentation (the division of larger areas of habitat into smaller areas) and accessibility.
As linear features increase on the landscape, access into previously inaccessible areas increases. In turn, greater accessibility means added opportunities for wildlife harvesting, increased predation rates, and a change in how people and wildlife use the land. Given the significant implications of added linear density, it is an effective tool in cumulative effects measurement.
Linear density can be estimated using satellite imagery together with project proposals and/or reports. Like surface disturbance, it can also be used with maps of values to determine other indicators such as access to high valued wildlife habitat.

Exempt Areas

Disturbances in some areas will not count. These include:

  • Highway corridors: within 1km of the Region's 3 highways
  • Within Municipal boundaries (LMU #14)
  • Within the "Klondike Highway Corridor" LMU (LMU#13)

 

Discussion: Surface Disturbance Measurement and Recovery

Which of the following should be included in the calculation of surface disturbance and cumulative effects recovery?

  1. Surface disturbances facilitate travel by wildlife and people. In forested areas, a surface disturbance can be considered recovered when vegetation growth is over 1.5 metres.
  2. Surface disturbance results in increased run-off and sediment loading. Recovery is when increased run-off and sediment loading has returned to pre-disturbance levels.
  3. Major surface disturbances can result in a change to the topography of an area. Recovery is when contours roughly match the original contours.

 

 

Let us know what you think!

Discussion: Linear Disturbance

Measurement of linear features as indicators of fragmentation and accessibility is difficult, as there are limitations on measurement.

Option 1: Linear features less than 1.5 metres wide are exempt from calculations. This is more reflective of the intent of tracking linear density, but measurement has proven to be inaccurate.

Option 2: Linear features less than 3 metres wide are exempt from calculations. Measurement using current technology is much more accurate, but the impact of smaller linear disturbances are ignored.

 

Let us know what you think!

Thresholds

The thresholds recommended in the Plan provide guidance on the acceptable limits of human-caused disturbance in every LMU. The designations give guidance about their intent, but they need to be able to be defined in a clear-cut, measurable, objective way. Thresholds for each designation achieve this.

These thresholds are not intended to be an absolute cap on activities. In the Integrated Stewardship Area, the Plan uses these levels to try and balance potential risks to ecological and cultural resources with economic development.


In order for indicators to be evaluated relative to an LMU’s thresholds, they need to be tracked. Some indicators can be periodically mapped and evaluated using satellite imagery. However, the status of indicators may need to be updated in between satellite-based re-evaluations. This may done using information in project proposals and project year-end reporting.

There are three threshold levels:

Precautionary threshold

 

  • Up to this point, disturbance is evaluated using coarse and preliminary mapping only.
  • Exceeding the precautionary threshold triggers more detailed disturbance mapping.
  • Only necessary if detailed disturbance mapping is missing.

Cautionary threshold

  • Means that disturbance indicators are close to reaching undesirable levels.
  • Provides an early warning signal.
  • Allows time for pro-active management to avert or limit potential impacts.
  • Management actions may include:
    • Prescribing specific practices to project proponents;
    • Researching the health of values that are at risk; and
    • Improving the indicator mapping.

Critical threshold

  • Represents the point at which the indicators have reached or surpassed acceptable levels.
  • Projects that could surpass the critical threshold for that LMU will be found not to conform to the Plan during a YESAA (Yukon Environmental and Socio-economic Assessment Act) screening/evaluation. This will influence the assessment and permitting stages of the project.

 

 

Cumulative Effects Framework

The Draft Plan needs a way to tie zoning, measured indicators and thresholds together to guide land use decisions. This is what we call the cumulative effects framework. Under this framework, proposed projects that would push disturbance levels for a Land Management Unit over its critical threshold may not conform to the Plan.

Disturbances for the region have not been recently determined. However, the Commission, in collaboration with the Yukon Government, Tr’ondëk Hwëch’in and others is using a computer model called ALCES to help estimate current disturbance levels and estimate them in the future. At this time, the model considers only disturbances from placer and quartz mining and exploration, and does not yet look at the interaction between these disturbances and values like moose or caribou. The Commission used preliminary results and considered their tolerance for further development to raft disturbance thresholds in the table below. They ensured that the threshold for each ISA exceeded current disturbance levels to allow for continued development.

 

 

 

 Designation

Management
Intent

Cumulative Effects Indicator

Precautionary Level*

Cautionary
 Level**

Critical
 Level

SMA I

No new disturbance

 

Tracking disturbance is unnecessary in the SMA I since no new disturbance is allowed.

SMA II
 

Disturbance only in connection to existing surface and sub-surface rights

 

Thresholds align with ISA I or ISA II, depending on the LMU. These are defined in those LMU’s Special Management Directions in Section 5.0.

ISA Zone I
 

Lowest development

Surface disturbance

0.04%

0.19%

0.25%

Linear density

0.04 km/km²

0.19 km/km2

0.25 km/km2

ISA
 Zone II
 

 Low development

Surface disturbance

0.15%

0.75%

1.0%

Linear density

0.15 km/km²

0.75 km/km²

1.0 km/km²

ISA Zone III
 

Moderate development

Surface disturbance

0.375%

1.875%

2.5%

Linear density

0.375 km/km²

1.875 km/km²

2.5 km/km²

ISA Zone IV

Highest development

Surface disturbance

0.75%

3.75%

5.0%

Linear density

0.75 km/km²

3.75 km/km²

5.0 km/km²
 

Discussion: Cumulative Effects Framework

As this is a draft plan, these thresholds may change based on improvements to the ALCES model, new disturbance mapping, and feedback to this Draft Plan. The Commission staff will continue to work with a Cumulative Effects Working Group (comprised of staff from the Commission, the Yukon Government, Tr’ondëk Hwëch’in and other cumulative effects researchers) and with an ALCES consultant to better understand and manage cumulative effects.

The cumulative effects frameworks in the North Yukon and Peel regions were developed primarily to balance oil and gas activity with the habitat needs of the Porcupine Caribou Herd. However, the Dawson Region is more complex with multiple industries and wildlife values. This added complexity has also been considered. To help focus ALCES modelling in the future, the Commission has also selected the key wildlife value for each ISA.

 

Let us know what you think!

Surface Disturbance

The footprint of this placer mine would include all disturbed areas, including settling ponds. Over time, as old disturbances recover, they may no longer "count" as being disturbed.

Linear Density

Roads, trails and cutlines over a certain width are considered "linear disturbance".

©2021 Dawson Regional Planning Commission

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