Urbanization and Forest Change
This indicator describes changes in land use that include loss of forest land, as well as increase in urbanization and accompanying impervious surface cover. Patterns of land use and land cover are one of the driving forces behind overall ecosystem health.

	Urbanization has increased across many low elevation watersheds and shoreline areas. Read more…
	Trends like speculative buying, forest conversion, and land fragmentation can cause degradation of our watersheds and aquatic resources. Read more…
	Changes in land use from a natural forested or vegetated state to urbanized areas can lead to considerable changes to watershed functions and aquatic resources over time. Read more…
	Education, technical assistance and economic incentives are being directed to retain forest and agricultural resources. Read more…

Introduction to the Urbanization and Forest Change Indicator

This indicator describes changes in land use between 1995 and 2000 in Puget Sound and 1992 and 1999 in the Georgia Basin. These changes include loss of forest, as well as increase in urbanization and accompanying impervious surface cover. Patterns of land use and land cover, in conjunction with the socioeconomic profile of the seven million people who live in the Puget Sound Georgia Basin, are some of the main driving forces behind overall ecosystem health.

Both urban development and loss of forest cover have a profound influence on the physical, chemical and biological quality of local streams, rivers and estuaries.²⁶ The loss of forest cover and increase in urbanization can dramatically alter the hydrology of local watersheds, which can significantly affect flooding, aquatic species and water quality.

Puget Sound Georgia Basin Land Cover Change by Watershed
Cumulative Change: 1995-2000 (WA), 1992-1999 (BC)

Click on the maps below to view a larger version. From the larger map, drill down to detailed maps of individual watersheds.

    

What Functions Does Natural Land Provide Humans?^{1, 25}

A landscape is a mosaic of patterns, similar to what you might see when flying in a plane as you gaze below. The manner in which rain and snow – and accompanying pollutants – move across a landscape and inevitably to water, varies widely. This depends on:

• The complexity and nature of living soils (soil composition, which in turn governs how fast water goes through)
• The relative compaction of the surface (tilled agricultural soils, native forest land, clearcuts, impervious development)
• How fragmented the patterns are (large contiguous tracts or smaller pieces intersected by development or other disruption, called fragmentation)
• The extent of impervious surfaces, as a percentage of a watershed
• The nature and extent of chemicals used in and around these landscapes

Landscapes, in their natural state, offer humans and other species an extraordinary array of environmental "services," all of which are irreplaceable without a cost taxpayers would be unwilling to bear. Quite simply, these services are necessary for our survival. For example, the manner in which plants use sunlight (photosynthesis) creates oxygen for us to breathe.

A well functioning ecosystem will:

Filter and Purify Water²⁷

• Soil particles and living organisms in water and soil filter, adsorb and absorb some pollutants and metals
• Wetlands remove 20-60 percent of metals in water, trap and retain 80-90 percent of sediment from runoff and eliminate 70-90 percent of entering nitrogen
• Streamside vegetation filters sediments and stores and transforms excess nutrients and pollutants carried in runoff from adjacent lands. It can reduce nitrogen concentration in water runoff and floodwater by up to 90 percent, and reduce phosphorous by 50 percent
• Microorganisms use or break down nutrients, metals and other chemical contaminants in the water

Maintain Freshwater Flows in Rivers and Streams

Freshwater flows provide a buffer against floods in winter and droughts in summer.

Provide Self-Sustaining Habitats for Myriad Species

• Local salmon runs are an important indicator of healthy watersheds
• Birds, frogs and even orcas depend on habitats maintained by the condition of the surrounding landscape.

Pollinate Crops and Plants

Bees, moths, butterflies, beetles, birds, mammals and reptiles help plants bear fruit and grow. Up to one half of all U.S. fruit and grain crops require pollination to produce their crops, including Washington's apple crops.

Store Carbon

Plants, trees and soil all store carbon dioxide, a primary global warming gas.

Build Soil and Grow Food

Provide Raw Materials for Our Entire Economy

Regulate Gases and Our Climate

Forest conditions affect carbon and nitrogen cycles, and help regulate temperature, precipitation and other ecosystem processes.

Provide the Basis for Medicines and Genetic Resources

Provide Cultural, Psychological and Recreational Amenities

Changing the Landscape and How It Functions Locally

The natural functions of soils and vegetation are disrupted by soil compaction from construction, using impervious surfaces for building and roads, and building in patterns that create isolated habitat sections or "patches of natural vegetation and land cover." Accordingly, when we build over wide swaths of land and remove or disturb essential habitat or habitat corridors, we directly affect local biodiversity.

In addition, changing as little as 10 percent of the surfaces of our watersheds to more impervious forms changes the flow patterns of streams and rivers.²⁸ This has several effects:

• Typically results in much more direct delivery of pollutants to local surface waters
• Increases flooding in the wet seasons while the dry seasons see a drop in the water table and further loss of flow in the streams and rivers
• Increases erosion, stream-bed scour, and increased deposition of sediments in downstream salmon spawning and shellfish growing areas

Click on the images below to view a larger version.

Graphic: Pre-Development Puget Sound Lowland Forest

Source: LOW IMPACT DEVELOPMENT Technical Guidance Manual for Puget Sound. Puget Sound Action Team, Washington State University Pierce County Extension. January 2005. Graphic by AHBL Engineering.

Graphic: Developed Puget Sound Lowland Forest

Source: LOW IMPACT DEVELOPMENT Technical Guidance Manual for Puget Sound. Puget Sound Action Team, Washington State University Pierce County Extension. January 2005. Graphic by AHBL Engineering.

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