Increase biodiversity to reduce tick populations

While evidence of biodiversity’s value is mounting, little has been done to generate practical solutions from that information. “What we haven’t done — and I don’t think anybody has done — is take those (research) results and model them on a landscape. It would be a powerful tool.”

Sacha Spector, Director of conservation science for Scenic Hudson Biodiversity impacts Lyme disease

KFL&A is in a high risk zone for Lyme disease. Most people get Lyme disease through bites from nymphal ticks which are as small as poppy seeds. The nymphs are abundant from May through July, but may emerge as early as April. In Ontario, approximately 70% of all cases are reported in June, July, and August which coincides with both greater participation in outdoor activities and increased presence of nymphal ticks. 

Image: CDC

To protect yourself from ticks, begin by learning to identify ticks—only blacklegged ticks (Ixodes scapularis) carry the Lyme bacteria. Visit the KFL&A Public Health website for more information and for protective measures.

Learn tick behaviour. Ticks don’t fly, jump, or drop on you from above. But they’re particularly good at hitchhiking, using a behaviour called questing to latch on when you brush against vegetation on which they’re lurking. Sandra Bushmich, associate dean of agriculture, health, and natural resources at the University of Connecticut says “Larval ticks will climb about an inch up, nymphs will quest about six inches up, and adults will climb about a foot up on the vegetation waiting for someone to brush by.”

Negar Elmieh, in a review of ticks in Canada and health risks from exposure, suggests the following  personal protection measures. 

  • While outdoors: Walk on cleared trails; wear light-coloured clothing covering arms and legs (to easily identify ticks); tuck clothing (e.g., pants into socks, shirt into pants), and wear closed-toed shoes to create a barrier for skin; apply insect repellent; wear permethrin-treated clothing; conduct regular checks for crawling ticks. 
  • After spending time outdoors: Thoroughly check for ticks (top 10 tick hiding spots) and remove ticks using appropriate methods; check pets for ticks; change clothes; put clothes worn outdoors in the dryer on high heat to kill ticks; take a shower/bath.

Canadian Pediatric Society ranks the effectiveness of tick repellents. Farmer’s Almanac shares seven natural tick repellents.

How effective is the conventional advice for protecting yourself from Lyme disease?

If you google ticks, the conventional landscaping advice includes:

  • Mow lawns short
  • Rake and dispose of leaves
  • Remove stones, wood, brush piles, water, and other habitat features 
  • Create a barrier between wilder areas of your yard and lawns

But do tick control measures actually reduce your risk of contracting Lyme disease? 

The Tick Project sought to determine whether neighbourhood-based prevention can reduce human cases of Lyme and other tick-borne diseases.. The result of their five year study? The number of ticks dropped, but the number of cases of Lyme disease did not.

When discussing the results, longtime tick researcher Dr. Felicia Keesing said

“The tick research community has never found an intervention that actually reduces cases in people. Our study is consistent with previous evidence suggesting that reducing tick abundance in residential areas might not reduce incidence of tick borne diseases in humans.”

Prevalence of the Lyme bacteria is greater in ticks in areas lacking biodiversity.

“But what if the loss of biodiversity made you sick…more likely to be exposed to infectious diseases?”

Richard Ostfeld,  Richard Ostfeld, Lyme Disease—The Ecology of a Complex System

Adult ticks, who mostly feed upon white-tailed deer, drop off the deer and lay their eggs on the forest floor. The following year the eggs hatch into larvae. Since deer don’t carry the Lyme bacteria, the larvae will only get infected and be carriers if they feed on an animal that carries the bacteria, which is most often a white-footed mouse (Peromyscus leucopus).

While tick larvae may also feed on other small mammals like squirrels and opossums, these creatures have much better grooming habits than mice—grooming off and eating most of the ticks who try to feed on them. More biodiversity means more alternative hosts like squirrels and opossums (yes, opossums have been spotted in Kingston, hopefully snacking on ticks!) More biodiversity also means more predators such as owls, birds of prey, snakes and foxes also help control the mouse population.

As a result, in areas lacking biodiversity the prevalence of the Lyme bacteria in ticks is higher because mice populations are higher while their competitors, their predators, and the creatures that deal with ticks efficiently are lacking. This means that if you’re bitten by a tick in an area lacking biodiversity, chances are greater that you’ll contract Lyme disease than an area with ecological diversity.

Read more about the ecology of Lyme disease.

Increase biodiversity to reduce tick populations

Image: New York State Integrated Pest Management 

Blacklegged ticks are most active in the spring and fall, although you can often find them active year round if conditions are right (above 2 Celsius in the winter, or when cool and damp in the summer). 

Image: Preferred habitats of different tick species, New York State Integrated Pest Management

Ticks, though most common in densely wooded areas (67%) and the transitional edge habitat between woodlands and an open area (22%), can be found anywhere. On our lawns. In the park. On a trail. On the golf course. Different species of ticks prefer different habitats. While Blacklegged ticks prefer the forest and forest edge, American Dog ticks can survive in warm, dry locations such as roadsides, trails and lawns. And Lone Star ticks are equally at home in lawns as in the forest.  

So what can we do?

  • Create paths: One metre wide woodchip, gravel, stone, or stone dust paths reduce the chance you’ll brush against a questing tick and creates a barrier which, due to heat and dryness, is difficult (but not impossible) for ticks to cross. Tick nymphs have leaky cuticles, or outer covers, that rapidly lose moisture. As a result, they can’t survive in environments with lower than 80% humidity for more than eight hours.
  • Mow based on your comfort level: Evidence is lacking on the relationship between mowing and ticks. KFL&A says that “Tall grass on its own would not typically harbour blacklegged ticks.” A study of coastal Maine microhabitats showed grasses to be the poorest quality habitat for ticks even when not mown. Taller grasses supported a higher abundances and diversity of native bees, with no impact on the tick population. Lawns were mown weekly to a height of 11.2 cm (4.4 inches), every two weeks to a height of 12.5 cm (5 inches), or every three weeks 15.1 cm (6 inches). No ticks were collected on any of the lawns. (Lerman 2018) 
  • Replace invasive shrubs with native shrubs: Japanese Barberry (Berberis thunbergii), Honeysuckle (Lonicera spp.), and Multiflora Rose (Rosa multiflora) create microclimates that are especially good habitat for ticks and their hosts and reduce the complexity of a food web, lowering small mammal species diversity and reducing the species and number of arthropods. Eliminating Japanese Barberry reduces the number of infected ticks by nearly 60%. (Clark 2019)
  • Design in patios, decks, and playspaces: Ticks prefer shady, humid environments. Locating patios, decks, paths, and play areas in open, sunny areas reduces the possibility of encountering a questing tick.
  • Increase habitat for squirrels, opossums and other small mammals: When a diversity of birds and mammals are present, blacklegged ticks can feed on non-mouse hosts that are less efficient at transferring the Lyme disease bacteria. Here’s a fun report card on the effectiveness of different animals on controlling ticks. Virginia opossum (the only marsupial found in Canada) gets an A+, but squirrels are also effective. While chipmunks carry the Lyme disease bacteria, they also eat baby mice so may help keep mouse populations (the primary culprits in the spread of the Lyme bacteria) in check.
  • Increase habitat for snakes and predatory mammals: Predators, such as foxes, owls, birds of prey, and snakes eat mice, reducing the tick population. 
  • Attract insect eating birds: While birds are generalists and aren’t proven tick eaters, you can attract insect-eating birds with flowering insectary plants which greatly increase the likelihood that predators and parasitoids will hang around and help out with pest management.
  • Plant a native meadow, prairie patch, or butterfly garden: While data is limited, meadows appear to harbour few blacklegged ticks except along narrow edges with woodlands, dense vegetation, and stone walls. Choose native meadow plants to support a diversity of butterflies and other insects, bats, hummingbirds, salamanders, toads, snakes, and turtles, but not encourage deer or mice. (Stafford, 2007)
  • Increase vertical complexity: Multiple layers of habitat with diverse species—canopy, understory, shrub layer, groundcover, and deadwood—offer more food and shelter for a wider variety of organisms (Bourdin, 2022), and increase the dilution effect (reducing mouse-tick interactions and subsequent disease risk).
  • Plant (and eat) lots of alliums: Alliums, both non-native (ornamental alliums, garlic chives, chives, garlic, leeks, onions) and native (Allium tricoccum, Allium schoenoprasum, Allium cernuum, Allium canadense) may repel ticks. Garlic supplements, in a Swedish study, significantly reduced the number of tick bites in soldiers.
  • Learn to protect yourself from ticks.

“At the very least, submitting to the inevitability of the tick’s hunger is a condition for my entrance into the spring landscape of a Montanan forest. If that forest is to remain wild, which is to say, dynamically alive and open to the full range of evolved relationships constituting Cenezoic existence, then I am called to refrain from altering this landscape in such a manner that ticks, along with any of the other species indigenous to it, would simply be eradicated from it. Leopold’s insight about the importance of the mountain lion to the mountain deserves a timely extension. To have faith in a mountainside of Palouse Prairie, dotted with bitterroots, shooting stars and anemones, as well as home to bunch grass and grazing deer, requires as a corollary my faith in ticks, my affirming their participation in this particular and unique instantiation of the living world.”

James Hatley, Blood Intimacies and Biodicy: Keeping Faith with Ticks


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