The Impact of Deforestation on Air and Water Quality in North-Central Colorado: A Comprehensive Analysis

Deforestation has a significant impact on the quantity and quality of air and water, as well as the health of forests in North-Central Colorado. Forests are essential to the state's economy, culture, and lifestyle, and our watersheds of origin are subject to various human and environmental pressures. The pine beetle, deforestation, wildfires, mining, increased recreational use, invasive species, and climate change are all potential sources of future impacts on source water quality. Operational changes to the Colorado-Big Thompson (C-BT) project, including proposed water supply transfers to the Horsetooth Reservoir, are also potential sources of future impacts on water quality. Until now, climate policy has focused only on carbon stocks and sequestration to assess the potential of forests to mitigate global warming.

However, when forest cover, structure, and composition change, changes in biophysical processes (water and energy balances) can increase or decrease the climatic effects of the carbon released by forest biomass on the ground. The net climate impact of carbon effects and biophysical effects determines outcomes for forest and agricultural species, as well as for the human beings that depend on them. The evaluation of the net impact is complicated by the disparate space-time scales at which they operate. Here we review the biophysical mechanisms by which forests influence climate and synthesize recent work on the biophysical climate forcing of forests at all latitudes. Then, we combined published data on the biophysical effects of deforestation on climate by latitude with a new analysis of the climate impact of CO2 on aerial forest biomass by latitude to quantitatively assess how these processes combine to shape local and global climate. We found that tropical deforestation leads to strong net global warming as a result of both CO2 and biophysical effects.

From the tropics to a point between 30° N and 40° N, the biophysical cooling caused by standing forests is both local and global, adding to the global cooling effect of CO2 sequestered by forests. At mid-latitudes of up to 50° N, deforestation leads to modest net global warming, as the warming caused by the carbon released from the forests exceeds a small opposite biophysical cooling. Beyond 50° N, large-scale deforestation leads to net global cooling due to the predominance of biophysical processes (particularly the increase in albedo) over the warming caused by the release of CO2. Locally, at all latitudes, the biophysical impacts of forests far exceed the effects of CO2, promoting local climate stability by reducing extreme temperatures in all seasons and hours of the day. Current carbon-focused metrics do not adequately capture the importance of forests both for mitigating global climate change and for local adaptation of human and non-human species, particularly in light of future climate warming. Rainfall is also affected when fires that cause forest clearing pollute the air and release tiny particles known as aerosols into the atmosphere.

While aerosols can heat or cool air depending on their size, shape and color, high concentrations of aerosols that burn biomass directly affect local climate by increasing cloud formation but decreasing rainfall. Therefore, large wildfires have an effect of further reducing rainfall, making burned areas more prone to dryness and future fires. In partnership with IPAM and IEPS, Human Rights Watch conducted a total of 67 interviews with federal, state, and municipal health officials; healthcare providers; members of medical associations; academics with experience in health, environment, and climate; representatives of civil society organizations; and indigenous leaders from communities affected by smoke from deforestation-related fires. The source of data on deforestation and active fire sources is the National Institute for Space Research (INPE), while data on air pollution were obtained from SISAM (Health-Related Environmental Information System), a research project between INPE, Ministry of Health and Pan American Health Organization (PAHO). The source for hospitalizations is DATASUS (Computing Department from Brazilian Unified Health System). For example, malaria and snail-borne schistosomiasis have intensified due to artificial pools created by dams, rice paddies, drainage ditches or irrigation canals. Deep roots and high leaf area make forests very efficient at moving water from Earth's surface to atmosphere through ET (evapotranspiration), producing latent heat.

Only Texas could see a 25 percent decrease in rainfall after Amazon deforestation - affecting agricultural productivity among other sectors. From 30° N to 40° N up northwards - albedo dominates - leading to net biophysical effect cooling due to deforestation. Deforestation in these watersheds - often caused by agricultural or commodity production - can contaminate water sources causing floods or droughts - as well as higher water treatment costs. Until Brazil effectively curbs deforestation - fires are expected to return every year - destroying rainforest while poisoning air millions breathe. It is appropriate that International Day of Forests (March 2) & World Water Day (March 2) are side by side - since health these important resources often go hand in hand. Deep roots - high water use efficiency & high surface roughness allow trees to continue transpiring during drought conditions - dissipating heat.

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