This week, marine biologist Anjani Ganase reviews the scientific article “Reefs since Columbus” written by ecologist Dr. Jeremy Jackson (1997) highlighting the history of degradation of Caribbean marine ecosystems since the time of Columbus. The significant loss of key marine animals long before the advent of modern monitoring and research on coral reef health, indicates the problem of the shifting baseline and our failure to understand what a truly healthy (or unexploited) coral reef or marine environment might be like.
This article was first published in the Tobago Newsday on Thursday, October 27, 2016.
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“Large vertebrates such as the green turtle, hawksbill turtle, manatee and the extinct Caribbean Monk Seal were decimated by about 1800 in the central and northern Caribbean…” – Dr Jackson 1997.
|The thrill of sharing a protected reef with these Galapagos Sea Lions, Galapagos. UNESCO World Heritage Marine Site. Photo by Underwater Earth, XL Catlin Seaview Survey.|
When we observe an ecosystem for the first time – a coral reef, rainforest, wetland – that impression forever becomes our baseline against which we judge future changes to this environment. We often exclude the long-term history of impacts on these ecosystems, ignoring the major events in local, social or human history. What impact did the Industrial Revolution, World War II or organised large-scale agriculture have on our natural world? We forget that Europe was at one point covered in temperate forest; that New York City was originally a wetland; and before World War II access to Trinidad’s north coast beaches was only possible by donkey trails or boats. The challenge of shifting baselines becomes especially problematic when trying to convince legislators, communities and law makers of the need for protection, management and conservation, especially so when the degradation is slow and almost unseen within one’s lifetime. Unless you have experienced severe changes within a lifetime, then we assume that what we see was always the case. This is one of the reasons that we are unable to halt the degradation of many environments, both terrestrial and marine, around the world.
Here in the Caribbean, the field of coral reef ecology – recording reef health, monitoring marine diversity and function - is less than 70 years old. Already these coral reefs have over three hundred years of impact by man. Therefore the baselines for many scientists are marine environments that are essentially not pristine and already degraded. It is essential to place recent scientific monitoring of reef health in the context of the long-term history of Caribbean to truly grapple with the effects we have had on the marine organisms and ecosystems throughout the Caribbean. In his paper “Reefs since Columbus,” Dr. Jackson compiles the evidence of ships’ logs and fishery records in Jamaica and in other places in the Caribbean over 350 years; and as far back as possible to 1492 when Columbus arrived in the Americas.
|Majestic Manta Rays at home in the protected Komodo National Park, Indonesia. UNESCO World Heritage Marine Site. Photo by Underwater Earth, XL Catlin Seaview Survey.|
Marine mega fauna such as the turtles, manatees and rays are all sculptors of their seascape habitats, coral reefs, sea grass beds etc. They are the equivalent of the hippos, rhinos, elephants and the wildebeest of the Serengeti. When the colonizing English first arrived in Jamaica and Grand Cayman in the 1600s, they turned to sea turtle fishing for food. During this time, turtle harvesting was so intensive that by 1800s, the fishery for turtles had collapsed. Descriptions of seeing sea turtles in the wild went from this:
“But in those twenty leagues (100+ km), they saw very many more (sea turtles) for the sea was thick with them, and they were of the very largest, so numerous that it seemed that the ships would run aground on them and were as if bathing in them.” - Andres Bernaldez, 1494 in southeast Cuba
“I have not even seen most of these large animals (turtles), underwater for twenty years or more, and some of them never at all, despite thousands of hours SCUBA diving on and around coral reefs” – Dr. J. Jackson 1997
Dr Jackson calculated that populations of green turtles must have been somewhere between 6 and 600 million when the first Europeans arrived. He also speculates that the predators such as the sharks that fed on the juvenile turtles were immensely more numerous. Further, he leads us to reflect on the abundance and the health of the habitats - the sea grass beds, the coral reefs - that were required to support these turtle populations. And we arrive at a different baseline 500 years ago.
Today’s baselines are for habitats devoid of large numbers of turtles. One turtle can graze the same area as 155 sea urchins. Apart from the difference in quantities of sea grass being grazed, the mode of grazing - urchins are more selective of older blades – and the cycling of nutrients is different. Turtle faeces are often carried outside the sea grass beds affecting other habitats. The sea grass ecosystems have completely changed over the last three hundred years.
Human impacts are also from the land. Even though we have been studying the effects of land run off, erosion and eutrophication on the coral reefs in the last 60 years, there were signs of this disturbance already occurring since the time of the sugar cane boom in the Caribbean. Many island colonies were home to major plantations where massive stretches of land were cleared. This included Tobago. Scientists found clues to the long-term degradation on coral reefs in Barbados, where aerial photos of Barbadian reefs in the 1960s were already impoverished of the large branching Acropora corals in the shallows before the massive regional die off; most likely related to extensive land clearing events in the island’s history.
With regard to Caribbean fisheries, one island has a well-recorded history of the severe loss of fish life from overfishing – Jamaica. In the late 1800s the fisheries of Jamaica had peaked and collapsed. By the 1970s, the very small number of fish and their smaller sizes were seriously affecting food and the tourism industry.
Let’s look at another marine species. The last sighting of a Caribbean Monk seal in the northern Caribbean was recorded in 1952 somewhere between Jamaica and Nicaragua. It was declared extinct in 2008. They had been heavily hunted for oil.
“Studying grazing and predation on reefs today is like trying to understand the ecology of the Serengeti by studying the termites and the locusts, while ignoring the elephants and the wildebeests.” – Dr Jackson 1997
Today there are too few reefs that have large animals - sharks, turtles and rays. While the shifting baselines may be seen as convenient or a coping mechanism to maintain positive outlooks, there is a deeper truth. Humans have devastated the diversity of species on our planet. Will we take action when the only big marine life are in zoos or theme parks, or wake up after the reefs are devoid of fish and the corals dying or dead?
It’s not yet too late. What can we do as a species? What can we do as individuals?
Finally, I can only concur with the slim hope which Dr Jackson expresses at the end of his paper: “…really large marine protected areas on the scale of hundreds to thousands of square kilometers are vital to any hope of conserving Caribbean coral reefs and coral reef species. Can we restore damaged reefs? Can we control inputs from the land and harvesting? Can we manage what we do decide to invest in and use? … The people trying to answer (these questions) are... the only chance we have got.”
|The company of a lone eagle ray on Glover’s Reef, Belize Barrier Reef System. UNESCO World Heritage (in Danger) Marine Site. Photo by Underwater Earth, XL Catlin Seaview Survey.|
J. B. C. Jackson (1997). Reefs since Columbus, Coral Reefs, 16, Suppl: S23—S32