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3. Land Cover

Land cover and any change in coverage that has occurred over a six year period is summarized for the Rideau- Smiths Falls catchment and Town of Smiths Falls using spatially continuous vector data representing the catchment during the spring of 2008 and 2014. This dataset was developed by the RVCA through heads-up digitization of 20cm DRAPE ortho-imagery at a 1:4000 scale and details the surrounding landscape using 10 land cover classes.

Rideau - Smiths Falls Catchment

As shown in Table 5, the dominant land cover types in 2008 and 2014 were crop and pastureland and wetland, followed by settlement areas and woodland.

Table 5 Land cover (2008 vs. 2014) in the Rideau-Smiths Falls catchment
Land Cover20082014Change - 2008 to 2014
AreaAreaArea
HaPercentHaPercentHaPercent
Crop & Pasture136328133328-30-1
Wetland **1314271320276
> Evaluated(753)(15)(753)(15)(0)(0)
> Unevaluated(561)(12)(567)(12)(6)(0)
Settlement8431786518221
Woodland *82417826172
Transportation33873387
Water10221022
Aggregate471471
* Does not include treed swamps ** Includes treed swamps

From 2008 to 2014, there was an overall change of 42 hectares (from one land cover class to another) in the catchment, the majority of which can be attributed to the conversion of crop and pasture to newly developed settlements and emerging woodlands (i.e., plantations or early successional woodlands) (see Figure 12 for the location of the major changes).

Figure xx Dominant land cover change in the catchment (2008 vs. 2014)
Figure 12 Dominant land cover change in the catchment (2008 vs. 2014)

Table 6 shows the type of land cover change that has taken place between land cover classes/types from 2008 to 2014. Overall, the net area of crop and pastureland change (loss) is relatively small at 30 hectares relative to the remaining area of crop and pastureland in the catchment (as of 2014). Similarly, the net area of woodland change (gain) is also small at two hectares relative to the remaining area of woodland in the catchment (as of 2014).

Table 6 Land cover class change in the Rideau-Smiths Falls catchment (2008 to 2014)
Land CoverChange - 2008 to 2014
Area
HaPercent
Crop and Pasture to Settlement16.939.9
Crop and Pasture to Wooded Area13.231.1
Wooded Area to Unevaluated Wetland5.913.9
Wooded Area to Settlement49.4
Wooded Area to Crop and Pasture12.4
Unevaluated Wetland to Settlement0.71.7
Crop and Pasture to Unevaluated Wetland0.61.6
* Does not include treed swamps ** Includes treed swamps

Town of Smiths Falls

As shown in Table 7, the dominant land cover type in 2008 and 2014 was urban settlement (a mix of commercial, industrial and residential uses) and associated transportation infrastructure (roads and railways).

Table 7 Land cover (2008 vs. 2014) in the Town of Smiths Falls
Land Cover20082014Change - 2008 vs. 2014
AreaAreaArea
Ha.PercentHa.PercentHa.Percent
Settlement45644458442
Transportation1811818118
Woodland *155151611661
Crop & Pasture1211211311-8-1
Wetland**908908
> Evaluated(45)(4)(45)(4)(0)(0)
> Unevaluated(45)(4)(45)(4)(0)(0)
Water323323
* Does not include treed swamps ** Includes treed swamps

From 2008 to 2014, there was an overall change of 12 hectares (from one land cover class to another), the majority of which can be attributed to the conversion of crop and pasture to emerging woodlands (i.e., plantations or early successional forests) and new development in the Town of Smiths Falls (see Table 8 for a summary of these changes). Overall, the net area of crop and pastureland change (loss) is relatively small at 10 hectares relative to the remaining area of crop and pastureland in the catchment (as of 2014).

Table 8 Land cover change in the Town of Smiths Falls (2008 to 2014)
Land CoverChange - 2008 to 2014
Area
Ha.Percent
Crop and Pasture to Wooded Area8.469.5
Crop and Pasture to Settlement1.512.8
Settlement to Wooded Area0.97.7
Wooded Area to Settlement0.65.3
Unevaluated Wetland to Settlement0.54.7

Woodland Cover

In the Environment Canada Guideline (Third Edition) entitled “How Much Habitat Is Enough?” (hereafter referred to as the “Guideline”) the opening narrative under the Forest Habitat Guidelines section states that prior to European settlement, forest was the predominant habitat in the Mixedwood Plains ecozone. The remnants of this once vast forest now exist in a fragmented state in many areas (including the Rideau Valley watershed) with woodland patches of various sizes distributed across the settled landscape along with higher levels of forest cover associated with features such as the Frontenac Axis (within the on-Shield areas of the Rideau Lakes and Tay River subwatersheds). The forest legacy, in terms of the many types of wildlife species found, overall species richness, ecological functions provided and ecosystem complexity is still evident in the patches and regional forest matrices (found in the Middle Rideau subwatershed and elsewhere in the Rideau Valley watershed). These ecological features are in addition to other influences which forests have on water quality and stream hydrology including reducing soil erosion, producing oxygen, storing carbon along with many other ecological services that are essential not only for wildlife but for human well-being.

The Guideline also notes that forests provide a great many habitat niches that are in turn occupied by a great diversity of plant and animal species. They provide food, water and shelter for these species - whether they are breeding and resident locally or using forest cover to help them move across the landscape. This diversity of species includes many that are considered to be species at risk. Furthermore, from a wildlife perspective, there is increasing evidence that the total forest cover in a given area is a major predictor of the persistence and size of bird populations, and it is possible or perhaps likely that this pattern extends to other flora and fauna groups. The overall effect of a decrease in forest cover on birds in fragmented landscapes is that certain species disappear and many of the remaining ones become rare, or fail to reproduce, while species adapted to more open and successional habitats, as well as those that are more tolerant to human-induced disturbances in general, are able to persist and in some cases thrive. Species with specialized-habitat requirements are most likely to be adversely affected. The overall pattern of distribution of forest cover, the shape, area and juxtaposition of remaining forest patches and the quality of forest cover also play major roles in determining how valuable forests will be to wildlife and people alike.

The current science generally supports minimum forest habitat requirements between 30 and 50 percent, with some limited evidence that the upper limit may be even higher, depending on the organism/species phenomenon under investigation or land-use/resource management planning regime being considered/used.

As shown in Figure 13, 20 percent of the Rideau-Smiths Falls catchment contains 974 hectares of upland forest and 148 hectares of lowland forest (treed swamps) versus the 34 percent of woodland cover existing in the Middle Rideau subwatershed. In the Town of Smiths Falls, 17 percent of the drainage area contains 161 hectares of upland forest and 16 hectares of lowland forest (treed swamps). This is less than the 30 percent of forest cover that is identified as the minimum threshold required to sustain forest birds according to the Guideline and which may only support less than one half of potential species richness and marginally healthy aquatic systems. When forest cover drops below 30 percent, forest birds tend to disappear as breeders across the landscape.

Figure 34 Woodland cover and forest interior in the catchment
Figure 13 Woodland cover and forest interior in the catchment

Woodland (Patch) Size

According to the Ministry of Natural Resources’ Natural Heritage Reference Manual (Second Edition), larger woodlands are more likely to contain a greater diversity of plant and animal species and communities than smaller woodlands and have a greater relative importance for mobile animal species such as forest birds.

Bigger forests often provide a different type of habitat. Many forest birds breed far more successfully in larger forests than they do in smaller woodlots and some rely heavily on forest interior conditions. Populations are often healthier in regions with more forest cover and where forest fragments are grouped closely together or connected by corridors of natural habitat. Small forests support small numbers of wildlife. Some species are “area-sensitive” and tend not to inhabit small woodlands, regardless of forest interior conditions. Fragmented habitat also isolates local populations, especially small mammals, amphibians and reptiles with limited mobility. This reduces the healthy mixing of genetic traits that helps populations survive over the long run (Conserving the Forest Interior. Ontario Extension Notes, 2000).

The Environment Canada Guideline also notes that for forest plants that do not disperse broadly or quickly, preservation of some relatively undisturbed large forest patches is needed to sustain them because of their restricted dispersal abilities and specialized habitat requirements and to ensure continued seed or propagation sources for restored or regenerating areas nearby.

The Natural Heritage Reference Manual continues by stating that a larger size also allows woodlands to support more resilient nutrient cycles and food webs and to be big enough to permit different and important successional stages to co-exist. Small, isolated woodlands are more susceptible to the effects of blowdown, drought, disease, insect infestations, and invasions by predators and non-indigenous plants. It is also known that the viability of woodland wildlife depends not only on the characteristics of the woodland in which they reside, but also on the characteristics of the surrounding landscape where the woodland is situated. Additionally, the percentage of forest cover in the surrounding landscape, the presence of ecological barriers such as roads, the ability of various species to cross the matrix surrounding the woodland and the proximity of adjacent habitats interact with woodland size in influencing the species assemblage within a woodland.

Rideau-Smiths Falls Catchment

In the Rideau-Smiths Falls catchment (in 2014), 71 (36 percent) of the 346 woodland patches are very small, being less than one hectare in size. Another 114 (58 percent) of the woodland patches ranging from one to less than 20 hectares in size tend to be dominated by edge-tolerant bird species. The remaining 13 (six percent of) woodland patches range between 20 and 85 hectares in size and may support a few area-sensitive species and some edge intolerant species, but will be dominated by edge tolerant species.

There are no woodland patches in the catchment exceeding the 100 plus hectare size needed to support 60 percent of edge-intolerant, forest dependent, area sensitive birds; nor are there any patches that top 200 hectares, which according to the Environment Canada Guideline will support 80 percent of edge-intolerant forest bird species (including most area sensitive species) that prefer interior forest habitat conditions.

Table 9 presents a comparison of woodland patch size in 2008 and 2014 along with any changes that have occurred over that time in the catchment. An increase (of 11 ha) has been observed in the overall woodland patch area between the two reporting periods with most change in woodland area occurring in the 50 to 100 hectare woodland patch size class range.

Table 9 Woodland patches in the Rideau-Smiths Falls Catchment (2008 and 2014)
Woodland Patch Size Range (ha)Woodland* PatchesPatch Change
200820142008 to 2014
NumberAreaNumberAreaNumberArea
CountPercent HaPercentCountPercent HaPercentCountHa
Less than 1 73363647136364-2
1 to 2011658493511145845547-2-38
20 to 501153543711534735-7
50 to 100118082113614156
Totals201100963100198100974100-311
* Includes treed swamps

Town of Smiths Falls

Table 10 presents a comparison of woodland patch size in 2008 and 2014 along with any changes that have occurred over that time in the Town of Smiths Falls. An increase (of six hectares) has been observed in the overall woodland patch area between the two reporting periods with most change in occurring in the 20 to 50 hectare woodland patch size class range.

Table 10 Woodland patches in the Town of Smiths Falls (2008 and 2014)
Woodland Patch Size Range (ha)Woodland* PatchesPatch Change
200820142008 to 2014
NumberAreaNumberAreaNumberArea
CountPercentHaPercent CountPercent HaPercentCountHa
Less than 1 32571383058127-2-1
1 to 202239995820388749-2-12
20 to 5024593424784419
Totals5610017110052100177100-46
* Includes treed swamps

Forest Interior

The forest interior is habitat deep within woodlands. It is a sheltered, secluded environment away from the influence of forest edges and open habitats. Some people call it the “core” or the “heart” of a woodland. The presence of forest interior is a good sign of woodland health, and is directly related to the woodland’s size and shape. Large woodlands with round or square outlines have the greatest amount of forest interior. Small, narrow woodlands may have no forest interior conditions at all. Forest interior habitat is a remnant natural environment, reminiscent of the extensive, continuous forests of the past. This increasingly rare forest habitat is now a refuge for certain forest-dependent wildlife; they simply must have it to survive and thrive in a fragmented forest landscape (Conserving the Forest Interior. Ontario Extension Notes, 2000).

The Natural Heritage Reference Manual states that woodland interior habitat is usually defined as habitat more than 100 metres from the edge of the woodland and provides for relative seclusion from outside influences along with a habitat have centres that are more clearly buffered against the edge effects of agricultural activities or more harmful urban activities than those without.

Rideau-Smiths Falls Catchment

In the Rideau-Smiths Falls catchment (in 2014), the 198 woodland patches contain 39 forest interior patches (Figure 13) that occupy less than one percent (36 ha.) of the catchment land area (versus the five percent of interior forest in the Middle Rideau Subwatershed). This is below the ten percent figure referred to in the Environment Canada Guideline that is considered to be the minimum threshold for supporting edge intolerant bird species and other forest dwelling species in the landscape.

Most patches (38) have less than 10 hectares of interior forest, 32 of which have small areas of interior forest habitat less than one hectare in size.

Between 2008 and 2014, there has been a notable change in the number of woodland patches containing smaller areas of interior habitat (Table 11) with an increase of 18 woodlands containing less than one hectare of interior forest over the period. This has occurred as a result of the loss of interior forest habitat in the larger woodland patches in the catchment.

Table 11 Woodland Interior in the Rideau-Smiths Falls catchment (2008 and 2014)
Woodland Interior Habitat Size Range (ha)Woodland InteriorInterior Change
200820142008 to 2014
NumberAreaNumberAreaNumberArea
CountPercentHaPercentCountPercent HaPercentCountHa
Less than 1 1467393282721184
1 to 1062820566151849-2
10 to 30151235131130-1
Totals21100351003910036100181

Town of Smiths Falls

Table 12 presents a comparison of woodland forest interior in Smiths Falls between 2008 and 2014. The majority of woodlands have less than one hectare of interior forest with the only change occurring as a result of the ingrowth of one hectare of interior forest over that time.

Table 12 Woodland interior in the Town of Smiths Falls (2008 and 2014)
Woodland Interior Habitat Size Range (ha)Woodland InteriorInterior Change
200820142008 to 2014
NumberAreaNumberAreaNumberArea
CountPercentHaPercentCountPercent HaPercentCountHa
Less than 1 1110041001191472
1 to 101912811
Totals11100410012100510011

Wetland Cover

Wetlands are habitats forming the interface between aquatic and terrestrial systems. They are among the most productive and biologically diverse habitats on the planet. By the 1980s, according to the Natural Heritage Reference Manual, 68 percent of the original wetlands south of the Precambrian Shield in Ontario had been lost through encroachment, land clearance, drainage and filling.

Wetlands perform a number of important ecological and hydrological functions and provide an array of social and economic benefits that society values. Maintaining wetland cover in a watershed provides many ecological, economic, hydrological and social benefits that are listed in the Reference Manual and which may include:

Wetlands are habitats forming the interface between aquatic and terrestrial systems. They are among the most productive and biologically diverse habitats on the planet. By the 1980s, according to the Natural Heritage Reference Manual, 68 percent of the original wetlands south of the Precambrian Shield in Ontario had been lost through encroachment, land clearance, drainage and filling.

Wetlands perform a number of important ecological and hydrological functions and provide an array of social and economic benefits that society values. Maintaining wetland cover in a watershed provides many ecological, economic, hydrological and social benefits that are listed in the Reference Manual and which may include:

  • contributing to the stabilization of shorelines and to the reduction of erosion damage through the mitigation of water flow and soil binding by plant roots
  • mitigating surface water flow by storing water during periods of peak flow (such as spring snowmelt and heavy rainfall events) and releasing water during periods of low flow (this mitigation of water flow also contributes to a reduction of flood damage)
  • contributing to an improved water quality through the trapping of sediments, the removal and/or retention of excess nutrients, the immobilization and/or degradation of contaminants and the removal of bacteria
  • providing renewable harvesting of timber, fuel wood, fish, wildlife and wild rice
  • contributing to a stable, long-term water supply in areas of groundwater recharge and discharge
  • providing a high diversity of habitats that support a wide variety of plants and animals
  • acting as “carbon sinks” making a significant contribution to carbon storage
  • providing opportunities for recreation, education, research and tourism

Historically, the overall wetland coverage within the Great Lakes basin exceeded 10 percent, but there was significant variability among watersheds and jurisdictions, as stated in the Environment Canada Guideline. In the Rideau Valley Watershed, it has been estimated that pre-settlement wetland cover averaged 37 percent using information provided by Ducks Unlimited Canada (2010) versus the 21 percent of wetland cover existing in 2014 derived from DRAPE imagery analysis.

Using the same dataset, it is estimated that pre-settlement (historic) wetland cover averaged 32 percent in the Middle Rideau subwatershed versus the 27 percent of cover existing in 2014. This decline in wetland cover is also evident in the Rideau-Smiths Falls catchment (as seen in Figure 14) where there has been a 10 percent decrease in the area of wetland cover from pre-settlement times to the present (as summarized in Table 13).

Figure xx Catchment wetland cover
Figure 14 Catchment wetland cover

While there has been a reported ten percent decrease in wetland cover in the Rideau-Smiths Falls catchment from pre-settlement times, the remaining wetland cover in 2014 remains above the ecological thresholds cited in the Environment Canada Guideline. Nonetheless, in order to maintain critical hydrological and ecological functions along with related recreational and economic benefits provided by these wetland habitats in the catchment, a “no net loss” of currently existing wetlands should be employed to ensure the continued provision of tangible benefits accruing from them for landowners and surrounding communities.

Table 13 Wetland cover in the Middle Rideau subwatershed and Rideau-Smiths Falls catchment (Historic to 2014)
Wetland CoverPre-settlement20082014Change - Historic to 2014
AreaAreaAreaArea
HaPercentHaPercentHaPercentHaPercent
Rideau-Smiths Falls178937131427132027-468-26
Middle Rideau268153222127272222827-4587-17
Rideau Valley 13085237------7469821-56154-40