Plants with (Alternative) Benefit(s)
Keywords: carbon source, carbon sink, photosynthesis, carbon sequestration, hydrological restoration, wildlife habitat
To select appropriate plant material, landscape horticulturalists need to consider the potential benefits of plants to humans and, more importantly, to the wider ecosystem network.
Landscape horticulturalists can look to their local and natural ecosystems for examples of how to effectively select plants and manage landscapes. Let’s first look at the role of forests, also known as the lungs of the earth, as an example of the ecological roles and benefits of plants.
“Forests can act as either carbon sources or carbon sinks.
- A forest is considered to be a carbon source if it releases more carbon than it absorbs. Forest carbon is released when trees burn or when they decay after dying (as a result of old age or of fire, insect attack or other disturbance).
- A forest is considered to be a carbon sink if it absorbs more carbon from the atmosphere than it releases. Carbon is absorbed from the atmosphere through photosynthesis. It then becomes deposited in forest biomass (that is, trunks, branches, roots and leaves), in dead organic matter (litter and dead wood) and in soils. This process of carbon absorption and deposition is known as carbon sequestration” (Government of Canada, 2022).
Video credit: How Trees Capture and Store Carbon, (The Woodland Trust, 2021)
“Climate change is expected to have a profound impact on the carbon balance of Canada’s forests. The biggest short-term impacts will result from changes in disturbance regimes. For example, scientists at Natural Resources Canada’s Canadian Forest Service predict that the forest area annually burned in Canada is likely to double by the end of the century, resulting in large emissions of carbon.
More frequent and longer-lasting droughts are expected to contribute to this increase. Similarly, increases in the area and intensity of insect outbreaks are expected to cause carbon losses. Already, climate change, in the form of warmer winters, has contributed to the major infestation of the mountain pine beetle in British Columbia and its recent spread over the Rocky Mountains into Alberta. A key question is whether the insect will be able to expand its range through Canada’s boreal forests.
Some aspects of climate change, such as longer growing seasons or greater concentrations of carbon dioxide in the atmosphere, are expected to increase tree productivity (at least initially). A warmer, wetter climate may also enhance decomposition rates. Northern regions of Canada are expected to warm faster than more southerly areas, resulting in the melting of permafrost; this may release methane from frozen soils and initiate the decomposition of previously frozen organic carbon” (Government of Canada, 2022).
Now, let’s take a look at an example from Foresty, a horticulture-adjacent industry for factors to consider when making land management decisions and the impact of decisions on the environment, economy and society.
“Forest management is not one size fits all. Different forest types, different ownership and different objectives create a vast mosaic of forest management across the Oregon landscape. In 2015 the City of Astoria entered into a voluntary carbon project that sold carbon credits from the management of their watershed. The purpose of this forest carbon project was to generate non-timber revenue that diversified income streams from traditional timber harvest within the watershed. Managing a forest for carbon credits takes a specific kind of management that requires a lot of planning upfront, along with a number of partners to make it all come together”(Oregon Forests, 2022)
Video Credit: Different Forests. Different Goals. Carbon Storage (Oregon Forests, 2022).
Let’s think about a few of the most common work environments for a landscape horticulturist. Some typical work environments for landscape horticulturalists include residential gardens, commercial or industrial greenways, city or municipality boulevards or parks, or even botanical gardens.
Wherever the work environment is, it’s part of our role as landscape horticulturalists to contribute to the ecosystems that we disrupt through our work. Equally important, landscape horticulturalists need to advocate plant selections that sequester carbon, improve hydrology restoration and promote wildlife habitat. So, how can landscape horticulturalists support carbon sequestration in our plant selection process? The answer is obvious: plant more plants, and in particular, plant more trees! However, with changing climates and unpredictable climatic events, it can be challenging to select plants that will survive in the landscape over the long term.
Two resources to support landscape horticulturalists’ plant selection choices are:
- Canada’s Plant Hardiness Zones which now include climate modelling projects for plant species: Canada Plant Hardiness Zones – Climatic Modelling
This site explores the relationship between plants and climate across Canada. One portion of the site is dedicated to plant hardiness zone maps, which have traditionally been used by gardeners to help select which plant species to grow in their area. Another part of the site presents maps and models that summarize the climatic requirements of thousands of plants from across North America. A final aspect of the site gathers data and provides summaries about plants that occur in your area. - i-Tree Species, this tool helps you select the most appropriate tree species based on their potential tree benefits and your geographic area: i-Tree Species
Users can start by choosing their location, then select and rank the importance of 0–10 of the desired tree benefits, such as carbon storage, air pollution removal, stormwater impacts, building energy conservation, air temperature reduction, ultraviolet radiation reduction, pollen allergenicity, and wind reduction.
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