By Mary Free, Extension Master Gardener
HAPPY POLLINATOR WEEK!
As we celebrate pollinators this week, let’s take time to reflect on some of the threats pollinators face and to consider specific actions we, as individuals, can take to help support pollinators. This four-part series will focus on Climate Change (Part 1) and Residential Land Use (Parts 2, 3, 4).
Part 1. Climate Change
Human-induced climate change and human development—the conversion of natural lands to residential, commercial, and agricultural use—constitute the biggest threats to biodiversity and pollinators.
Perhaps it is easier to visualize the human impact on our planet if you consider that in 2020, global human-made mass exceeded all living biomass! The mass of plastic alone was twice that of living animals (Elhacham et al., 2020). Sixty percent of the mammals on earth were comprised of domestic livestock (dominated by cattle and pigs), while only 4% were wild (the remaining 36% were humans); 72% of the birds on the planet were domesticated poultry, while only 28% were wild (Bar-on et al., 2018). Adding to this imbalance between human-controlled and wild biomass is the toxicity of human-made mass and the pollution produced by human activities.
Global warming and extreme weather events; degradation, fragmentation, and loss of natural habitats; stress on fresh water resources; and use of chemicals and pesticides—all these have led to an overall decline in pollinator and other wild animal populations. Pollinators not only aid in the reproduction of over 85% of flowering plants and over two-thirds of our crop species, but are themselves food for arthropods, many birds, frogs, salamanders, and other animals. A 2019 study found that rapid rates of insect decline could “lead to the extinction of 40% of the world’s insect species over the next few decades (Sánchez-Bayo & Wyckhuys, 2019).” Extinctions on that scale would have a cascading effect on the plants and other animals that depend on these insects, including humans.
DID YOU KNOW?
According to the National Oceanic and Atmospheric Administration, the 10 warmest years in the historical record all occurred since 2014, with 2024 forecast to be warmer than 2023, the warmest year since global records began in 1850.
According to Climate Central, since 1970 the length of the growing season (freeze-free season) across Virginia has increased 15–50+ days depending on location.
Over time, native plants and their pollinators have developed a mutualistic relationship that depends on the synchronization of their life cycles. Global warming can affect this synchronicity. When this happens, both plants and pollinators can suffer.
Warmer winters can disrupt the dormancy of overwintering insects or advance the growing season. One study found that spring ephemerals that emerged earlier than their pollinators showed a lower seed count due to decreased pollination services (Kudo & Ida, 2013). When a plant species is not available during pollinator migration, foraging, or breeding, its pollinators may become less fit, more vulnerable to disease and parasites, and experience reproductive problems. Pollinator specialists that forage for pollen on specific species are at highest risk when their demand for pollen from their host plant(s) does not coincide with supply (Maglianesi et al., 2020). Specialist bees comprise 28% of Virginia’s native bee population ranking it second among eastern states with the highest percentage of specialist bees (Jarrod and Droege, 2020), which are most vulnerable to mismatched host plant/insect life cycles.
Climate change is responsible for more than desynchronization. Extreme weather events—extended heat or drought, radical temperature fluctuations, less snow cover, flooding, and high winds—also affect the health and life of plants and pollinators. The less productive a plant is in terms of nectar and pollen quality and quantity and blooming period, the fewer pollinators it can support. According to the Pollinator Partnership, 60% of the western monarch population died because of the severe rain and wind storms California experienced in 2023.
DID YOU KNOW?
Planting multiple species within a given genus on which specialist insects rely could limit potential phenology mismatches due to climate change or help ensure the viability of some host plants during extreme weather events. Pollinator conservationist Heather Holm says that in her garden she grows three species of dogwoods with slightly different bloom times to help ensure a pollen supply for the five bee species that specialize on just collecting dogwood pollen. Similarly, for monarchs, planting both natives Asclepias incarnata and Asclepias tuberosa, with their different blooming periods and habitat requirements, would increase the chances that one of the species would remain a viable host in a season that was wetter or drier or hotter than normal. Monarch egg counts are also higher when more than one milkweed species is present.
Successfully combatting global warming requires action on a global scale through the cooperation of governments, businesses, and other entities. Besides pressing legislators to act, there are steps we can take to reduce our individual carbon footprints. Some of these are commonsense practices that you may already follow. Others may not be practical or affordable for your particular situation. But every action that you take can help!
Energy
In 2022, the United States Environmental Protection Agency (EPA) reported that electric power, of which 60% was generated by burning fossil fuels, produced 25% of U.S. greenhouse gas emissions. Another 13% of emissions came from the use of fossil fuels for heating and cooking and of gases for refrigeration and cooling in residential and commercial buildings as well as the handling of solid waste. Also included in these numbers is the energy used by lawn and garden equipment. (See Part 3. Residential Land Use: Lawns for more information.)
What You Can Do
- Use less energy—turn off appliances and lights when not in use. Set your thermostat as high as is comfortable in summer and as low as is comfortable in winter. To save energy, the EPA recommends a setpoint of >78° in summer and <70° in winter and adjusting temperatures 5°–8° degrees (up in summer, down in winter) from the normal setting, when you are away from home for several hours. However, if you have a heat pump, setting back its thermostat when it is in heating mode “can cause the unit to operate inefficiently, so a moderate setting is the most cost-effective practice” in cooler weather.
- Look for ENERGY STAR products when it comes time for replacements or new purchases.
- Insulate your roof and, if feasible, install solar panels.
- Use a zero-carbon or renewable energy provider if available.
- Plant trees!
DID YOU KNOW?
Besides their wildlife benefits and beauty, trees can save energy and reduce costs. Utah State University recommends planting:
• deciduous trees to shade a building’s east side from 7 to 11 a.m. and to shade the west side from 3 to 7 p.m. during June, July, and August
• smaller deciduous or low-limbed evergreen trees northeast of the building to shade in early morning and northwest to shade late afternoon
• evergreen trees and shrubs as a screen to block cold winter winds.
For more information, including diagrams, see Planting Trees for Energy Conservation.
© Elaine Mills
Visit MGNV’s Tried and True Native Plant Selections for the Mid-Atlantic for fact sheets on native trees. Also watch MGNV’s Sustainable Landscaping Basics video. Part 2 of this series—Residential Land Use: Impervious Surfaces—provides more information about tree plantng.
Food
Crop and livestock production uses more than a third of the world’s land surface and nearly 75% of freshwater resources (Brondízio et al., 2019). Inadequate pollination resulted in 3%–5% lower crop productivity and lowered the economic value by up to 31% from what could be achieved if pollinators were abundant (Smith et al, 2022). EPA estimates that the agriculture sector generates about 10% of greenhouse gas emissions in the U.S., although others estimate a higher carbon footprint for industrial agriculture when it includes the production of chemicals used, operation of equipment and buildings, and transportation of food products.
According to the United Nations Environment Programme, sustainable farming uses 20%–56% less energy and organic farming creates about 64% fewer emissions than conventional agriculture. Using an ecosystem management approach in sustainable agriculture can conserve pollinator diversity and improve the quality and quantity of yields (Katumo et al., 2022).
What You Can Do
- Buy sustainable food products. Buy local and seasonal foods. Avoid meat produced on factory-farms and eat more plant-based food. Buy and prepare only what you can eat.
- Create a kitchen garden or work a community plot to grow some of your food (watch the videos Introduction to Vegetable Gardening Parts 1 & 2).
- Eliminate use of or reuse grocery store plastic bags and recycle them and other food packaging.
- Compost food scraps.
DID YOU KNOW?
According to the EPA, food scraps comprise 24.1% of U.S. municipal solid waste and are responsible for 58% of landfill methane emissions. Composting reduces landfill emissions, reduces solid waste management costs, and recycles organic material into a quality soil amendment.
If you are interested in doing your own composting, then visit our MGNV resources page: National Learn About Composting Day or watch the MGNV video: The Art of Composting: How to Make Your Own Black Gold. Otherwise,
• Alexandria residents can register for the city’s curbside composting pilot program (April 2023–2025). City residents also can drop off food waste free of charge at the Food Waste Drop-Off Stations, located at the Farmers’ Markets in the City.
• In Arlington County, residential customers in single-family homes can place food scraps in the green curbside organics cart provided. Other County residents can drop off food scraps at the Trades Center.
Transportation
In the United States, 94% of fuel used for transportation is petroleum-based and contributes 28% of direct greenhouse gas emissions, the highest of all sectors.
What You Can Do
- Drive less often. Walk or cycle when possible.
- Carpool or use (preferably electric) public transportation.
- Buy a hybrid or electric vehicle, when it comes time for replacement.
- Travel by train instead of plane (or car) on available routes.
DID YOU KNOW?
According to its FY2023 Environmental Sustainability Annual Report, Metro prevented more than 78,000 metric tons of carbon dioxide equivalent from entering the atmosphere – equivalent to emissions from about 200 million miles driven in an average gasoline-powered passenger vehicle.
A 2022 U.S. Department of Transportation study found that electrified trains generate fewer emissions than other modes of transportation. “For each city pair and mode, operational emissions were estimated by calculating the roundtrip per-passenger-mile fuel efficiency and emissions.” On one round-trip between Boston and New York, travel by car or plane generated more than five times the emissions of the all-electric Acela. Even if a person took the diesel rail, they left a lower carbon footprint—about half of the emissions of a car or airplane round-trip between Los Angeles and San Diego and about one-fourth the emissions of a plane or car between St. Louis and Chicago.
If you would like more information on how climate change affects the plants on your property and actions you can take to mitigate or adapt to changes in our climate, then watch MGNV’s Climate Conscious Gardening video.
Next up: Part 2. Residential Land Use: Impervious Surfaces
References
10 ways you can help fight the climate crisis. May 4, 2022. United Nations Environment Programme.
A Guide to Energy-Efficient Heating and Cooling. 2009. EPA 430-K-09-004. United States Environmental Protection Agency.
Baniassadi A, Manor B, Yu W, Travison T, Lipsitz L. 2023. Nighttime ambient temperature and sleep in community-dwelling older adults. Science of The Total Environment. Volume 899. ISSN 0048-9697. doi: 10.1016/j.scitotenv.2023.165623.
Bar-On YM, Phillips R, Milo R. Edited by Falkowski PG. 2018. The biomass distribution on Earth. Proceedings of the National Academy of Sciences (PNAS). 115(25): 6506–6511. doi:10.1073/pnas.171184211. [PDF/EPUB]
Brondízio E, Díaz S, Settele J, Nigo HT. 2019: Global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
Elhacham E, Ben-Uri L, Grozovski J, Bar-On YM, Milo R. 2020. Global human-made mass exceeds all living biomass. Nature 588: 442–454. doi: 10.1038/s41586-020-3010-5.
Jarrod F & Droege S. 2020. Pollen Specialist Bees of the Eastern United States.
Freimuth J, Bossdorf O, Scheepens JF, Willems FM. 2022. Climate warming changes synchrony of plants and pollinators. Proc. R. Soc. B. 28920212142. doi: 10.1098/rspb.2021.2142.
Global Action on Pollination Services for Sustainable Agriculture. Food and Agricultural Organization of the United Nations. (accessed May 12, 2024).
How tweaking your diet can help save the planet. August 23, 2021. United Nations Environment Programme.
Janousek WM, Douglas MR, Cannings S, Graves TA. Edited by Inouye BD. 2023. Recent and future declines of a historically widespread pollinator linked to climate, land cover, and pesticides. Proceedings of the National Academy of Sciences (PNAS). 120(5):1–9. doi: 10.1073/pnas.2211223120. [PDF/EPUB]
Katumo DM, Liang H, Ochola AC, Lv M, Wang Q-F, Yang C-F. 2022. Pollinator diversity benefits natural and agricultural ecosystems, environmental health, and human welfare. Plant Diversity, 44(5): 429-435. ISSN 2468-2659. doi:10.1016/j.pld.2022.01.005.
Kudo G, Ida TY. 2013. Early onset of spring increases the phenological mismatch between plants and pollinators. Ecology. 94(10): 2311–2320. doi: 10.1890/12-2003.1.
Kuhns M. Planting Trees for Energy Conservation: The Right Tree in the Right Place. Utah State University/Forestry Extension. [PDF with graphics]
Lindsey R, Dahlman L. 2024. Climate Change: Global Temperature. Climate.gov. National Oceanic and Atmospheric Administration.
Maglianesi MA, Hanson P, Brenes E, Benadi G, Schleuning M, Dalsgaard B. High levels of phenological asynchrony between specialized pollinators and plants with short flowering phases. Ecology. 2020 Nov;101(11):e03162. doi: 10.1002/ecy.3162. Epub 2020 Sep 27. PMID: 33460104.
Maynard-Bean E, Kaye M, Wagner T, et al. 2020. Citizen scientists record novel leaf phenology of invasive shrubs in eastern U.S. forests. Biological Invasions 22: 3325–3337.
National Land Cover Database 2019 (NLCD2019) Statistics for 2016. Multi-Resolution Land Characteristics (accessed May 7, 2024).
Programmable Thermostat. U.S. Department of Energy.
Sánchez-Bayo F, Wyckhuys KAG. 2019. Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation. 232: 8-27. ISSN 0006-3207. doi;10.1016/j.biocon.2019.01.020.
Simon MC, Mittelman A, Solman G, Gilman S, Henning O, Raymond A, Blatnica R. 2022. Carbon Dioxide Emissions from Four Real World Inter-City Passenger Trips: A Comparison of Rail, Air, and Road Travel Modes by City Pair. Publication: FRA-RRD30-2022-0001. Federal Railroad Administration. U.S. Department of Transportation.
Smith MR, Mueller ND, Springmann M, Sulser TB, Garibaldi LA, Gerber J, Wiebe K, Myers SS. 2024. Pollinator Deficits, Food Consumption, and Consequences for Human Health: A Modeling Study. Environmental Health Perspectives. 130(12). doi: 10.1289/EHP10947. [PDF]
Son J. 2020. Lawn Maintenance and Climate Change. PSCI. Princeton University.
Sources of Greenhouse Gas Emissions. United States Environmental Protection Agency. Last updated April 11, 2024. (accessed May 11, 2024).
Tabuchi H. 2024. Trains Are Cleaner Than Planes, Right? The New York Times.
Talt G. 2020. The ComPOSTer: How much can composting help in solving the climate challenge? [UPDATED]. Sustainable Composting Research at Princeton.
Threats to Pollinators. Pollinator Partnership. (accessed MAY 4, 2024).
UN Report: Nature’s Dangerous Decline ‘Unprecedented’; Species Extinction Rates ‘Accelerating.’ 2019. United Nations Sustainable Development GOALS. [see Brondízio et al., 2019 for full report]
Webster T. 2024. FY2023 Environmental Sustainability Annual Report. Washington Metropolitan Area Transit Authority.