Chapter 3 – Land Use Change
Release Date: November 2012
The Credit River Watershed has undergone substantial change over the last two centuries. Before European settlement, the dominant land cover type in the watershed was forest and wetland. Agricultural expansion and forestry during the late 19th and early 20th centuries resulted in loss of forest habitat, with woodland cover (which includes upland forest, swamp and successional) reaching a low of 16.3 percent in 1954 (Department of Planning and Development 1956). Since 1951, extensive reforestation efforts by landowners, municipalities and other agencies have contributed to the reversal of forest cover decline. Conversion of agricultural and forested land to urban, however, has continued at a rapid rate.
Urbanization is one of the biggest challenges facing the Credit River Watershed today. In fact, between 1996 and 2006 the population in the Credit River Watershed grew from 573,000 to 758,000 (George Morris Centre 2009). That is an increase of 32 percent (185,000 people) over ten years. Population growth in the watershed is expected to continue. In the Region of Peel, for example, population forecasts anticipate the number of residents to increase from 1.3 million in 2011 to 1.4 million by 2031 (Growth Management in Peel 2008).
Land Use/Cover Status
More than one third of the Credit River Watershed is currently comprised of agriculture and open space, however, this number is declining as agricultural land is converted to urban land cover. This decline is most prevalent in the Lower Watershed (Figure 1), although most regions of the Credit River Watershed are experiencing rapid urbanization (George Morris Centre 2008).
The Integrated Watershed Monitoring Program (IWMP) recognizes land use/cover change as a major stressor to the ecological integrity of the Credit River Watershed. Following agriculture and open space, urban areas (28%) represent the next highest proportion of land cover in the watershed. This is followed by upland forest (17%),meadow/successional (9%), wetland (7%), aggregate(2%) andaquatic (1%) (Figure 2).
Land cover and land use differ considerably among physiographic zones. (Figure 3) Urbanization is highest in the Lower Watershed, where the majority of the population lives, while agriculture and open space comprise significant proportions of the Middle and Upper Watershed. Natural cover (forest, wetland and meadow/successional) also comprises a major portion of the Middle and Upper Watershed. Although the percent urban land cover is lower in the Upper and Middle Watersheds compared to the Lower Watershed, urbanization in the Upper and Middle Watershed may have a greater impact on the overall health of the Credit River because these regions are the headwaters of the river.
As population growth continues, the watershed’s natural features and functions are undergoing increasing stress. With urbanization comes an increase in impervious, or hardened, surfaces such as roads, rooftops and parking lots. These hardened surfaces have an impact on how water moves to streams and how contaminants get into our waterways. Because impervious surfaces restrict water from infiltrating into the ground, rain and snowmelt move very quickly over land, picking up pollutants from roads and parking lots along the way, increasing stream temperatures and increasing potential for flooding in nearby streams. This in turn affects the health of fish communities and other aquatic life. In addition to impacts on surface water, groundwater and aquatic life, urbanization also places pressure on terrestrial communities through loss and fragmentation of habitats and through introduction of non-native species.
Research has shown there is a limit to urbanization beyond which the environmental structure and function of the Credit River Watershed becomes seriously impaired (CVC 2007). By studying long-term monitoring results from both urban and rural environments, CVC can learn how land use/cover change, specifically urbanization, influences the ecological integrity of the Credit River Watershed. This information can inform management decisions aimed at improving the health of the watershed.
In Chapter 4, we will explore recent climate patterns in the watershed and look at how trends in air temperature and precipitation compare to long-term records. Do these patterns indicate climate change is occurring in the Credit River Watershed? Stay tuned for Chapter 4 of the Credit River Watershed Health Report.
Department of Planning and Development. 1956. Credit Valley Conservation Report. Toronto.
CVC (Credit Valley Conservation). 2007. Credit River Water Management Study Update: Making it Work
George Morris Centre. 2008. Statistical Profile of Agriculture in the Credit River Watershed.
George Morris Centre. 2009. Demographic Profile of the Credit River Watershed.