Graywhale entangled in driftnet
Many people in Europe (and in other parts of the world) take their natural environments for granted in terms of believing that their forest, mountain, lake and river wildernesses have remained more or less untouched for hundreds if not thousands of years. That of course is an illusion. Human habitation has always changed the environment, and often very drastically. That goes for the American Indians and Australian Aborigines as much as for the Romans, Greeks and Celts. Animals were hunted to extinction or the brink thereof for food or rituals, and forested areas were denuded to build houses, ships or establish agricultural land. And, as an article in this week’s New Scientist reports, freshwater and marine life shared the same faith.
The article’s conclusion is that humans have been depleting fish stocks not just for decades but for many centuries. This finding is based on a new historical survey undertaken by marine scientists and presented at a conference being held this week in Canada.
“We are discovering that human pressure on marine life was much earlier, much larger and much more significant than previously thought,” says Poul Holm, an environmental historian at Trinity College Dublin in Ireland. “We now know that there was major commercial exploitation of fisheries, doing huge damage to fish populations, back in medieval times and even before. The idea that it is only modern fishing technology that has done damage turns out to be completely wrong.”
The Oceans Past II conference in Vancouver, Canada, is part of the decade-long Census of Marine Life, a global effort to understand the past, present and future of ocean life. The census is due to be completed next year.
To reconstruct the state of the oceans centuries and even millennia ago, researchers are combining population modelling techniques with historical records, such as ships’ logs, restaurant menus, paintings, diaries, legal documents and even tax returns. For example, in 1153 a Moroccan geographer called al-Idris wrote that the north Atlantic Ocean contained “animals of such great size that the inhabitants of islands use the bones and vertebrae in place of wood to build houses”.
Much of the work presented at the conference concludes that fish stocks were already depleted before the industrial exploitation of the 20th century made the situation even worse. “We used to think that if we could get fish stocks back up to the levels of the 1970s we would be well on the way to recovery,” says Holm. This now seems to be an optimistic idea.
James Barrett and Jen Harland of the University of Cambridge reported at the conference that freshwater fisheries in much of Europe were already in decline 1000 years ago, causing fishers to switch to marine fishing. By 1500, says Maria Lucia De Nicolo of the University of Bologna, Italy, coastal fish stocks were disappearing and deep-sea fishing began, with trawling starting in the mid-1600s. By the early 1800s, the once super abundant European herring fishery had collapsed.
Other studies show that whale numbers were also plummeting at this time. By the early 1800s, wind-powered whaling ships had virtually wiped out a population of nearly a million bowhead whales in the eastern Arctic Ocean. Meanwhile, in the 18th century there were an estimated 27,000 southern right whales off New Zealand, but by 1925, before the introduction of factory ships, they had been reduced to about 25 reproducing females, according to Emma Carroll of the University of Auckland.
What that means is not only that a few marine species have gone extinct, but entire marine ecosystems may have been depleted beyond recovery. That does not bode well for the future, especially since nowadays we’re not only confronted by overfishing but also other ecological problems such as the effects of aquaculture, the warming and acidification of oceans or marine pollution. And: we’re not exactly quick learners. Therefore: given that it has taken thousands of years for us to come to a point where our impacts on the natural ecology has become global and ubiquitous, it probably will take at least hundreds of years for the oceans to return to a new equilibrium – and they will be very different then.
[The New Scientist: Human fishing spree goes back 1000 years; Image: Bob Talbot, Marine Photobank]