Why Planting Trees Isn’t Enough on Its Own
Planting a thousand trees on a site means little for the climate if they’re surrounded by an excessive amount of freshly poured Portland cement and imported steel, since that combination often leaves a project net-negative overall. This is the reality of embodied carbon, the total greenhouse gases emitted during a material’s extraction, manufacturing, transportation, and installation. While operational carbon can be reduced over a park’s lifetime, embodied carbon locks in the moment materials arrive on site, which is why landscape architects need to treat carbon as strictly as a financial budget.
The Worst Offenders for Embodied Carbon
Concrete is the foundation of landscape architecture, but manufacturing Portland cement is responsible for roughly eight percent of all global CO2 emissions, meaning specifying thick, oversized slabs when a thinner profile would suffice quietly destroys a carbon budget. Firing clay brick requires maintaining kilns at around 2,000 degrees Fahrenheit for days, an energy intensity per square foot astronomically higher than natural, uncut stone or permeable aggregates. Steel edging, galvanized planters, and aluminum structures require massive mining and smelting energy, resulting in extreme embodied carbon per pound of material.
Fly Ash and Slag Substitution
Landscape footings and flatwork rarely need 100 percent pure Portland cement. Requiring a ready-mix plant to replace thirty to forty percent of the Portland cement with recycled fly ash, a coal plant byproduct, or slag slashes the carbon footprint of a concrete pour while actually increasing its long-term strength.
Relative Carbon Impact by Material
Standard concrete paving carries a very high embodied carbon impact, best mitigated by specifying a thirty percent fly ash mix or using permeable crushed aggregate instead. Fired clay brick carries a high impact, best mitigated by using reclaimed or salvaged historical brick. Imported natural stone carries a moderate-to-high, transport-heavy impact, best mitigated by sourcing regional stone within roughly 500 miles. Sustainably harvested timber carries a negative impact, acting as a carbon sink, best realized by using FSC-certified wood instead of steel for boardwalks and structures.
Where the Calculation Work Goes
Cross-referencing Environmental Product Declarations, calculating material volumes, and translating cubic yards of concrete into kilograms of CO2 equivalent is a monumental task by hand. CalcType’s Embodied Carbon Calculators calculate the carbon footprint of hardscape materials directly and compare the climate impact of concrete versus timber side by side.