Fragmentation of the Muskoka environment — an insidious threat to biodiversity
By Patricia Arney | September 26th 2026
Fragmentation is one clear environmental threat that an integrated management plan could control in the Muskoka River watershed.
When drafting any environmental management plan, one important objective is to identify and reduce threats to environmental resilience. Fragmentation, a frequent consequence of development, is an obvious issue to address. But what do we mean by fragmentation, and what does it threaten?
Fragmentation is simply the division of a large patch of undisturbed natural habitat that supports numerous species, into two or more smaller patches.
Roads are the most obvious culprits, but power lines, all-terrain vehicle-snow machine trails, logging-agricultural sites or other disturbances, which “cut through” previously undisturbed habitat can all be fragmenting agents. These cuts reduce the extent of interior habitat while increasing the extent of edge habitat.
Plants and animals adapted to deep interior forests recognize the difference and will not survive in edge habitat. The number and sizes of undisturbed patches is just as significant for maintaining biodiversity as is the total area of natural habitat.
Fragmentation differs from “habitat loss” but its impact is not necessarily a lot less.
Muskoka is still substantially forested, but the 2023 Muskoka Watershed Report Card indicated considerably more areas of fragmentation than the 2018 Report Card. Patch size, or size of unfragmented natural areas, is very important to many wildlife species.
A study by Dawn Burke and Erica Nol of Ontario bird species that occupy “interior forests” showed reproductive success was dependent on the amount of interior forest within patches of forest habitat. Ovenbirds and Wood Thrushes were more sensitive than Veery and Rose-breasted Grosbeaks, but all four did better in larger habitat patches. They concluded that undivided forest tracts of at least 500 hectares are needed to sustain populations of most native interior forest birds (used as an indicator of forest health).
No research yet provides similar data for moose, deer, wolves, bear, hawks or skinks: the number of hectares of undisturbed natural area each requires to thrive or survive.
When roads, trails, rail or hydro lines cut through forests they limit the amount of space in which animals and birds may feed, breed and hunt. This may result in inbreeding and increased predation. The “cut” creates new edge habitat. Different species inhabit edges, often more predatory species, causing interior dwellers to die out.
Many interior dwelling species require 100 metres or more from an edge to survive, so Ontario’s Significant Wildlife Habitat Technical Guide stresses that consideration should be given to shape as well as area of patches with square or rectangular preferable to long narrow strips.
If patches of suitable habitat are connected by corridors enabling animal movement some effects of fragmentation can be reduced. A 2022 Natural Capital Inventory for Muskoka provides data on animal movement corridors with detailed information on white tailed deer. The report also outlines significant work needed to map corridors for amphibians, cervids and other mammals.
Given the amount of development in Muskoka already, the best approach to mitigate fragmentation of habitats may be to identify animal movement corridors and protect them well. The Ministry of Transportation has built crossings over some highways but more may need to be done.
Muskoka Watershed Council considers that fragmentation of any large natural area in Muskoka should be considered a negative impact on watershed health until research is available to properly identify the size and nature of “undisturbed” natural areas required to protect biodiversity.
Large undisturbed parcels of land are vital for preserving Muskoka’s biodiversity. An integrated watershed management plan could protect such habitat and identify corridors to provide safe crossings when new roads into backlots, or to reach water access cottages, are proposed.
Consider this before you plan that next “cut” in the forest!
This article was first published by MuskokaRegion.com.
Patricia Arney
This is article No. 38 in the current series, Nurturing Our Watersheds, from Muskoka Watershed Council. Its author is Patricia Arney, former long-time resident of Muskoka and member of Muskoka Watershed Council. The series is edited by Peter Sale.