Tom Karwin, On Gardening | Securing Biodiversity in the Garden, Part 2

This column follows our recent overview of biodiversity, which refers to the variety of all living things (animals, plants, fungi and microorganisms) and their interactions. Biodiversity involves three levels: species, genetic and ecosystem diversity.

Paperwhite (Narcissus papyraceus 'Ziva') This is a perennial bulbous plant native to the Mediterranean region, from Greece to Portugal plus Morocco and Algeria. The strongly fragrant white flowers are borne in bunches and attract numerous pollinators This plant grows with minimal care in the garden, but it is often grown as a house plant and forced to flower at Christmas. (Photo by Tom Karwin) — Paperwhite (Narcissus papyraceus ‘Ziva’) This is a perennial bulbous plant native to the Mediterranean region, from Greece to Portugal plus Morocco and Algeria. The strongly fragrant white flowers are borne in bunches and attract numerous pollinators This plant grows with minimal care in the garden, but it is often grown as a house plant and forced to flower at Christmas. (Photo by Tom Karwin)

Species diversity refers to changes within a given species of plants or animals, as the result of sexual propagation, natural or human hybridization, or mutation.

Genetic diversity is an evolutionary process in which organisms adapt gradually to changes in the environment.

Ecosystems provide habitats for organisms that interact with their environment. Ecosystem diversity refers to the array of ecosystems within a given area. There are many types of ecosystems: deserts, tropical rainforests, mangroves, wetlands, coral reefs, estuaries, mountains, grasslands and several others.

Losses of biodiversity result from human activity: habitat reduction, climate change and environmental pollution.

We have become aware of biodiversity losses. For example, the dramatic reduction in the number of monarch butterflies is generally understood to result from a loss of habitat.

Biodiversity losses extend to large numbers of plants and animals, as indicated in Part 1 of this series. There are growing concerns about these losses, which damage the plants and wildlife, and ultimately threaten society’s dependence on the natural environment.

These concerns are motivating programs at the state, national and global levels to slow the rate of biodiversity loss, and to reverse that process.

A current initiative, reported in the California Native Plant Society: “Tribal and community leaders across California are coming together to champion four national monument campaigns that would total at least 700,000 new acres of conserved lands. The four campaigns call for new national monuments or expansions for Molok Luyuk, the San Gabriel Mountains, Chuckwalla, and now Medicine Lake Highlands.” Land conservation protects ecosystem diversity and contributes greatly to the protection of native plant and animal species and their habitats.

Citizen participation in such efforts demonstrates an opportunity for interested individuals to contribute to securing biodiversity.

Today’s column focuses on the loss of biodiversity at the garden level, and the role of individual gardeners to secure biodiversity in the garden.

The photo gallery for this column depicts plants in my garden that are now in bloom or on display. They are representative of plants selected as consistent with securing biodiversity.

Bromeliad (Billbergia brasiliensis) This native of Brazil has colorful inflorescences that bear red bracts and flowers of dark violet with golden stamens. The leaves, which are banded with silvery trichomes, form tightly rolled, forming flute-like rosettes that hold water. The plant reaches 24 inches tall. (Photo by Tom Karwin)

Our exploration of ways to secure biodiversity in the home garden refers to biodiversity loss’s three levels (species, genetic, and ecosystem) and three causes (habitat reduction, climate change, and environmental pollution).

Residential properties constitute reductions of the natural habitat, so gardeners should do all they can to maintain or restore wildlife habitats.

This involves multiple actions, which align with our general rule, “gardening with nature.”

First, incorporate native plants in support of wildlife, as scientist and author Doug Tallamy has advocated. His ideas and recommendations are accessible in his books (visit your local bookstore or Amazon) and online talks (find him on youtube.com). Native plants, especially those that are native to your specific area, are favorable to insects, birds, amphibians, reptiles and mammals. A good source of info on your garden’s native plants is available from the California Native Plant Society’s online plant selection tool, Calscape (calscape.org).

Another positive plant selection action is to remove invasive plants, which can crowd out native plants. An information resource for identifying invasive plants is the California Invasive Plant Council (www.cal-ipc.org).

While some gardeners enjoy dedicating their gardens entirely to plants that are native to their specific environment, planting for diversity can include non-native plants. A selection of different kinds of plants still should, collectively, provide nectar, seeds and cover for the wildlife. For both gardening successfully and securing biodiversity, select plants that are suited to your soil, land, climate, sun exposure and rainfall patterns.

Clearly, for the Monterey Bay area and California generally, this plant selection emphasizes drought-tolerant plants, which is a recognition of your ecosystem diversity. This approach allows the gardener to minimize irrigation of the garden, with hand-watering for newly installed plants and the use of efficient drip irrigation when required.

As plants adapt to environmental conditions in response to human-caused climate change, gardeners should take care to select plants that continue to be appropriate to their specific environment. This genetic change is a slow process, of course, but we are already seeing reports of plants and animals moving to areas that are new to them, to locate in more compatible warmer or cooler conditions.

Another important action to secure biodiversity in the garden is to eliminate artificial fertilizers and pesticides. These products might have short-term effectiveness, but, eventually, they pollute your garden and the environment and are often harmful to wildlife. Composting garden and kitchen waste and returning those nutrients to the garden is both cost-effective and part of securing biodiversity. The goal of keeping organic material in the garden includes composting the leaves of trees and shrubs, if only by leaving them to decompose naturally in the soil.

Sunburst Aeonium (Aeonium 'Sunburst') This cultivar grows 2 feet tall or more, develops leaves in stunning variegated rosettes 8 inches wide or (as shown) larger, and produces yellow inflorescences in spring and summer. Aeoniums are native to the Canary Islands. (Photo by Tom Karwin) — Sunburst Aeonium (Aeonium ‘Sunburst’) This cultivar grows 2 feet tall or more, develops leaves in stunning variegated rosettes 8 inches wide or (as shown) larger, and produces yellow inflorescences in spring and summer. Aeoniums are native to the Canary Islands. (Photo by Tom Karwin)

Advance your garden knowledge

California Native Plant Society’s Naturehood Gardening Webinars provide valuable plant-oriented information resources for home gardeners working to secure biodiversity. Visit their website (www.cnps.org/gardening/webinars) for an impressive list of recorded webinars, and info on upcoming webinars. Both recorded and live webinars are available without fees.

The next live webinar, “TLC for Native Trees,” will be presented at 5:30 p.m. Dec. 7. “California’s native trees are truly awe-inspiring — they can soar to majestic heights, live for thousands of years, and require dozens of people to circle them for a hug. But how do we care for them when they are in our garden?” Oscar Sanchez of TreeCare LA and the CNPS Horticulture Team, experts experienced with California native trees, will provide insights into tree care.

Enjoy your garden, and participate in the essential work of securing biodiversity.

Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a Lifetime UC Master Gardener (Certified 1999–2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view photos from his garden, https://www.facebook.com/ongardeningcom-566511763375123/ . For garden coaching info and an archive of On Gardening columns, visit ongardening.com for earlier columns or visit www.santacruzsentinel.com/ and search for “Karwin” for more recent columns. Email comments or questions to gardening@karwin.com.