Salt Spring is the last place one would expect to face a silent spring, but a new study points to dramatic changes taking place on the beautiful Gulf Islands, which are scattered across southern Georgia Strait.
Because of the fierce vigilance of local residents, the natural splendor of the islands has been preserved in the face of decades of development pressures. The protection of nature is so important, land owners who set aside wild habitat get tax breaks, and a poll a few years ago found 90 per cent of residents favoured preserving the islands as they are.
But two researchers from the faculty of forestry at the University of British Columbia have found that deer populations - which have grown dramatically because of hunting restrictions - are causing extensive environmental damage on the Gulf Islands.
There are now more deer on most islands than there were before European contact. As deer browse by the quiet roads that wind across the islands, they make for lovely nature pictures - but in reality they are destroying plants upon which many birds depend.
Tara Martin, an adjunct professor and her colleague, Prof. Peter Arcese, looked at birds, native plants and the density of black-tailed deer on 18 islands, including some, known as the San Juan Islands, on the U.S. side of the border.
What they found was an astonishing correlation between the number of deer browsing on any given island and the number of birds. Islands with high numbers of deer had half as many birds as those islands with low deer densities.
The researchers recorded 53 bird species on the islands and, of those they identified, 10 that were dependent on the understory vegetation deer like to feed on. When they did density estimates for those 10 species, they found all of them were more numerous on islands with low deer densities.
So, simply put, if you have lots of deer on an island, your song birds dramatically decline. Protecting deer by banning hunters may seem like a way to preserve nature. In fact it is the opposite. Bird species such as the fox and song sparrow, rufous hummingbird, spotted towhee, Bewick's wren and orange-crowned warbler are driven away from forests where the lush undergrowth has been mowed down by deer.
In some places, such as on Sidney Island, where fallow deer were set loose when a game ranch failed, the forest floor has been browsed down to dirt.
Even on islands where the understory seems healthy, the research indicates a sudden collapse of key plant species, such as ocean spray, could be coming. Deer focus on eating young plants. So while a quick inventory suggests a healthy ocean-spray population, in fact the plants that are there are all old. When the shrubs providing the seeds die, there will be a sudden collapse of the species.
"Indeed, our observations suggest that most if not all ocean spray on islands with high deer densities are relatively old and … [they]represent evidence of the island's outstanding extinction debt," states the report, published in the journal Biological Conservation.
"Given the mythical status of deer and antipathy towards hunting by many humans, a general sense of stewardship for plant and bird communities will need to be developed alongside a public awareness of the deleterious impacts of deer," the researchers conclude. "At present … deer in the San Juan and Gulf Island archipelago are browsing down our natural heritage. In the absence of active management, high browsing pressure by deer can be expected to result in local extinctions of herbaceous flora as well as iconic island birds."
Prof. Arcese was on Mayne Island on the weekend, talking at a public meeting about "the deer issue" in the hopes Gulf Islanders will start to understand the need for action.
"In particular, we're hoping that our work will help demonstrate to the public that failing to deal with [the deer overpopulation problem]… is in fact a de facto vote in favour of the potential extirpation of iconic native plants and birds," he said in an e-mail.
Hunting is banned on Mayne Island, and the current Denman Island official community plan calls for all parks and vacant Crown land to be closed to hunting. On other islands, large areas are closed to hunters, and anyone who does hunt needs to have two licences (a hunting licence and a Gulf Islands special-area licence) and $100,000 in public liability and property damage insurance. All of that is meant, of course, to discourage a 'blood sport' that many feel is not in keeping with the bucolic nature of the Gulf Islands.
In their dedication to preserving nature, Gulf Islanders have largely driven out hunters, creating an overabundance of deer. And now they are losing their song birds.