By Dr. Marcos Sommer
The sea and the atmosphere behave as infinite, swallowing the undesirable by-products of human activity. We are currently experiencing the fragility of marine balances, the answer is given to us by the almost dead Indian and Baltic Seas, the North Sea, whose fish resources are tragically declining, the Mediterranean severely affected and the dying reefs of the entire world.
• The 2008 reports are alarming: climate change, overfishing, pollution and social ignorance are taking many marine ecosystems to an extreme situation ...
The seas and oceans represent 71% of the Earth's surface, 360 million km2 and 97% of the terrestrial water resources.
They constitute a great source of biological and natural resources, comparable or even superior to tropical forests. They are also an economic resource and a reserve of energy sources, and are essential regulators of the Earth's climate, as well as highly productive systems that continuously recycle chemicals, nutrients and water. 40% of the world's population lives less than 60 km from the coast and 35 million people depend on fishing. The oceans are an essential source of food and employment, providing natural routes of communication, transportation and trade.
In the course of this year 2008, two studies have appeared that have revealed that human activity is seriously undermining the seas of the world.
Only 50 years ago the Ocean was still largely unspoiled wilderness. Today, however, overfishing and pollution, which in proportion more or less than 80 percent comes from land-based activities, are a threat to the health of the oceans, particularly the coastal areas, which are the most productive of the environment. marine (UNDP, 2007).
Fourteen years after entering the Law for the Oceans (United Nations Convention, 1994), the rupture of man's dialogue with the oceans becomes evident and notorious. The ever-widening and unsustainable gap between wealth and poverty threatens the stability of society as a whole and consequently the ecosystem of the oceans, the state of the oceans continues to worsen at alarming proportions. National and international commitments remain in declarations of intent and good will.
The Convention is one of the most important legal instruments of the 20th century. Conceived as a whole, recognizing that all the problems of the ocean space are closely related to each other and must be considered together, it establishes that the seabed and ocean floor and its subsoil beyond the limits of national jurisdiction are the common heritage of humanity that everyone has the right to use them and the obligation to protect them. It provides for mandatory dispute resolution, establishes the global legal framework for all activities carried out in the oceans and seas, and contains detailed rules that regulate all uses of the oceans and define the rights and responsibilities of States.
The oceans today, at the beginning of the 21st century, suffer serious degradation due to pollution, excessive fishing and the excessive urban coastal growth. What we know about them is disturbing, signs of the collapse are showing.
• Almost 80 percent of the fish stocks in the oceans are overfished or are being taken to their biological limit. Trawling techniques are harmful and destroy habitats for reproduction (FAO, 2005, Sommer, M., 2005).
• According to a new report by scientists and economists from the University of British Columbia, global fisheries subsidies amount to $ 30-34 billion a year. This huge aid has contributed to producing a global fishing fleet that is 250 percent larger than what is needed for sustainable fishing (Pauly, D., 2008).
• The European Union and Japan are the countries that assign the most subsidies for fishing (García, R. et. Al., 2003).
• Fishing fleets are 40 percent larger than the oceans can support. Fish represent at least one fifth of the total animal protein consumed on earth. About 95 percent of the world's marine fish harvest lives in coastal waters (FAO.org).
• Fishing provides in developing countries between 40 and 100 percent of the total animal protein needed by the population (FAO.org).
• Fishing exploitation is two to three times higher than the rate of reproduction of fish allows (Pauly D. et al., 1998).
• Commercial fishing reduced the world's large fish population by more than 90 percent, jeopardizing a vital source of protein (Waston R. & Pauly D., (2001).
• Fishing for low-value species has increased as the harvest of high-value species has stabilized or decreased, thus masking some of the effects of overfishing.
• One billion people depend on fish as a source of animal protein, and 150 million jobs come from fishing (FAO, 2005).
• The alteration of habitats is the consequence of activities such as dredging, landfills, uncontrolled dumping on the coast, construction and coastal roads, deforestation or damage caused by mass tourism. For example, despite the fact that coral reefs cover less than 0.5% of the seabed, 90% of marine species depend directly or indirectly on them. Reefs also protect the population living on the coast by acting as a protective element (Jackson, J.B.C., 1997).
• 60% of today's reefs are in danger of disappearing in the next 30 years if action is not taken. In particular, 85% of European coasts are in danger due to the development of infrastructures and buildings as well as due to natural causes (http://www.coral.org/divein).
• Around 150 whales, dolphins and porpoises die daily worldwide from entanglement with fishing gear, an annual average of 54,759 animals.
• The Atlantic, Pacific and Indian Oceans are slowly warming by an average of 0.06 degrees Celsius since 1955 due to the greenhouse effect. This climate change could lead to a rise in sea levels, which could reach between 9 and 95 centimeters by the end of the century (Parmesan, C. & Yohe, G., 2003, Thomas, CD, et al., 2004 .
• Approximately half of the world's coastal ecosystems (eg, including coral reefs, mangroves, and grasslands, etc.) are currently at risk of being fully degraded. Some deep-sea corals off the coast of Hawaii took up to 4,000 years to reach their current size (http://www.coral.org/divein).
• The oceans are becoming more and more acidic by absorbing carbon dioxide and plants are being affected by the increase in ultraviolet radiation (Buddemeier R. et al., 2004.
• The merchant marine is responsible for 4.5 of total carbon dioxide emissions, three more than previously thought.
• Ship traffic is the third largest cause of marine pollution. A study prepared by the UN concludes that the C02 emissions of the world merchant fleet reach 1,120 million tons per year and the forecasts do not seem promising: these emissions will increase by 30 percent between now and 2020 if no action is taken (UNEP / UNFCCC, 2002.
• It is estimated that more than 70 thousand synthetic chemicals have been discharged into the world's oceans. Only a small percentage of them have been monitored, and this corresponds to those related to human health and not to ecological impact.
• 80% of marine hydrocarbon pollution comes from activities carried out on land.
• The explosive increase in harmful algae, for example on the coasts of the USA, has involved, since 1991, costs close to 300 million dollars in losses due to the massive death of fish, public health problems and decreased tourism.
• There are currently more than 405 dead zones (extension less than 1 square kilometer and others reach 70,000 square kilometers) in the world due to the increase in pollution from inland and the loss of habitats capable of filtering pollution, which has caused the expansion hypoxic areas (Diaz RJ & Rosenberg R., 2008.
• The increase of foreign species in the coastal zones produces the interruption of the food chain by eliminating the native species. Every day, 3,000 species of plants and animals are transported in ships' ballast tanks.
• The world's oceans are home to more than 210,000 known forms of life. About 60 percent of the species live in the 60 km strip closest to the coast.
• Every year almost 160 new species of fish are found in the oceans and 1,700 animals and plants are cataloged.
• Half of the 6.3 billion inhabitants of the planet live in coastal areas, the great depths of the seas that cover 70 percent of the globe remain unknown.
• Global warming of the planet will have catastrophic effects on the oceans, slowing down their temperature regulating function. According to the International Panel on Climate Change (IPCC), the frequency and intensity of storms and other meteorological phenomena will increase, damaging marine ecosystems and their resilience (Gilman et al., 2006).
• Since 1980, the size of the global economy has tripled, while the population has increased by 30 percent to 6 billion people. Population increases and conversion for the purposes of urbanization, agriculture and aquaculture are leading to the reduction of mangroves, coastal wetlands, seagrass areas and coral reefs at an alarming rate.
The actions of man were always insignificant, compared to the magnitude of the marine ecosystem, everything was compensated by nature. The sea and the atmosphere behave as infinite, swallowing the undesirable by-products of human activity. The national use and the management of ecosystems has been in the forefront for years. We are currently experiencing the fragility of marine balances, the answer is given to us by the almost dead Indian and Baltic Seas, the North Sea, whose fish resources are tragically declining, the Mediterranean severely affected and the dying reefs of the entire world.
Fig .: 1. Human impact map, 17 aspects of global change that threaten 20 marine ecosystems are considered. This map allows us to design strategies and set priorities for the management of ecosystems (Source: Halpern B. S., et al. 2008).
The new atlas of the world's oceans (Halpern et. Al., 2008) reveals that human activities have had a strong impact on about 40 percent of their extent, leaving only about 4 percent of them relatively intact (Fig. 1.). The North Sea, the vicinity of Japan, the Caribbean, areas of the Mediterranean, the Persian Gulf or the Red Sea are some of the areas that have been the most damaging, although with climate change the situation is changing rapidly.
The author collected data from different sources and turned it into a model that assigned each square kilometer of ocean a unique value. This value reflects the set of impacts of all human-induced changes in that particular space. The result reveals that there is no area of the ocean that is completely safe from human activities. In each of the square kilometers of our seas, ecological changes are occurring due to anthropogenic causes, the study says. For this reason, in the scale of affection that they have used there is no value 0, but the lowest one refers to an impact less than 1.4. In this sense, and although many areas of the polar regions appear below that figure for now - also the Torres Strait, in northern Australia. The researchers warn that it is likely that, as climate change warms that area, the hand of man will eventually reach there - in all its destructive force. However, this analysis does not take into account air pollution, which is particularly high in the Arctic.
Where this the impact has reached 41 percent of the oceans, with a medium-high impact. And although the percentage where the affections have been very high only represent 0.5 of the seas, in absolute figures this percentage represents an area of more than 2.2 million square kilometers.
The most affected ecosystems are continental shelves, rocky reefs, coral reefs, grasslands and seamounts. And in addition to the aforementioned regions (eastern Caribbean, North Sea and waters of Japan), the researchers identify other areas with red alert: the China Sea, is its southern and eastern part, the east coast of North America, the Mediterranean Sea. , the Red Sea, the Persian Gulf, and parts of the western Pacific.
The publication by Halpern et al., Presents a database that reveals for the first time the magnitude, geographic extent and precise locations of ocean warming. With this information, citizens, researchers, politicians, etc., can begin to face the bigger problem, of understanding and anticipating how ocean warming will impact on marine ecosystems. Also, the results will help to rank an order of priority for marine conservation projects. For example, fishing areas can be modified and shipping routes redefined to reduce impacts on sensitive ecosystems.
Another of the most serious problems that currently arises is hunger, which is not only the need to eat but, as defined by food and health technicians, is the "continuous deprivation of sufficient food that prevents leading a life fury". According to data from the World Food Council, of the 6 billion inhabitants of the planet; every year, between 40 and 70 million die from causes related to hunger; of these 15 million are children; which means that 40 thousand children die of hunger every day.
In the effort that humanity has to develop to produce food, the ocean, which occupies about 75 percent of the earth's surface, offers great possibilities, since a large number of living beings develop in it.
Rapid technological advances and significant increases in human population over the last century have led to an extensive increase in the global exploitation of marine fishing industries, that is, the fishing capacity of individual vessels has increased. Radars allow boats to fish in fog and darkness; sonars pinpoint fish, and geolocation satellites pinpoint productive sites so vessels can return to them. Vessels can now drag nylon nets several kilometers long through the water and catch up to 400 tonnes of fish. 40 percent of what they catch is "waste" and is returned to the ocean. In the Northeast Atlantic alone, by-catch amounts to 3.7 million tonnes per year.
In 2006, 66.7 million tonnes of aquaculture products were produced in the world, compared to 93.1 million tonnes from extractive fishing. Global aquaculture production has grown significantly, going from 0.6 million tons in 1950 with a value of less than $ 0.5 million to 66.7 million tons in 2006 with a global value of 86, $ 2 million. It is projected to continue its expansion in the coming decades, reaching 100 million tonnes in 2030. Its contribution to the global supply of fish, crustaceans and molluscs grows year after year. According to the FAO, aquaculture production reached in 2006 a volume practically similar to world fisheries production for direct human consumption, not including the approximately 30 million tonnes of extractive fishery products not intended for human consumption (Fig. 2) ( Jackson, JBC plus 18 co-authors, 2001).
The great seas and oceans are perishable. Apart from the fact that all resources are currently fully exploited, access to those resources remains open to too many fisheries around the world.
According to FAO (2003), around 50 percent of the world's marine fisheries resources are fully exploited, 25 percent are over-exploited and the remaining 25 percent could withstand higher rates of exploitation . Despite the alert, the trend towards increasing overfishing, observed in the early 1970s, has not yet been reversed.
In the early 1990s, 13 of the 17 largest fishing grounds in the world were known to be depleted or in decline.
From gigantic swordfish to mighty bluefin tuna and from tropical grouper to Antarctic cod, industrial fishing has depleted the oceans. Not a blue border left standing, laments marine biologist Ransom
Fig. 2. Evolution of fishery production (fishing and aquaculture) in the world in the period 1950-2006 (FAO, 2003).
Myers of Dalhousie University of Canada. Myers and Boris Worm, from the University of Kiel (Germany), state in the journal Nature, a study in which they warn that industrial fishing has ended in just fifty years with 90% of the large fish, which only remain in the terrestrial oceans account for 10% of tunas, sharks, cod, fretans, groupers and swordfish (Myers RA and Worm B., 2003).
The two researchers have spent ten years gathering information on the most important fishing grounds. They have studied 47 years of censuses of large predatory fish on four continental shelves and nine ocean systems. His conclusion is that, if the trend does not change, human activity will lead these species to extinction in a few years. We would then live in a world without tuna, swordfish, groupers, sharks, cod are the megafauna, the great predators of the sea, and the species that we value the most. Their reduction not only threatens their future as species and that of the fishermen who depend on them, but it can also lead to a complete reorganization of ocean ecosystems with unknown global consequences (WormB. & Myers R.A., 2003).
The "widespread collapse" of marine ecosystems began to work. In the North Sea for example, the cod population has declined to such an extent that the industry is currently concentrated on haddock, a second-tier species in the ecological pyramid that cod usually eat. Pollock consumes small organisms such as copepods and krill. Krill also eat copepods. As the number of pollock decreases, the krill population expands and the copepod population drops dramatically. Copepods are the main food for juvenile cod, this prevents the recovery of the cod.
The industrial North financed the consolidation of the industrial fishing fleets of the developing South, in the 1960s and 1970s, this process accelerated the reduction of schools and led to half of the world catch taking place in those poor countries. Most of the fish production in these countries is exported, this is the reason why fish has not become a staple food in the southern hemisphere.
One of the major concerns of scientists is that the baselines (Pauly D., 1995, 1999) have changed for most marine ecosystems. This means that people now visit degraded coastal environments and consider them precious, not knowing what they were like before (Jackson, J.B.C et.al., 2001).
Today people go diving in California's kelp forests (Macrocystis pyrifera) that are devoid of black sea bass (Centropristis striata), broomtailed grouper (Mycteroperca xenarcha) and old California women (sheephead, Semicossiphus pulcher) that used to fill them. And these divers emerge with big smiles on their faces from having dived in a kelp forest. However, the reference lines in the literature show us the terrible change in this marine ecosystem. It is easy not to notice the changes in the oceans, for they are large and deep. However, the cases where the same oceanic patterns have been studied for a long time give us a glimpse of a very disturbing picture. For example, Jackson has documented the almost complete disappearance of the ecosystem that helped build his career: studying the coral reefs of Jamaica. About them he says: "There is virtually nothing left of the vibrant and diverse coral reef communities that I helped describe in the 1970s. Between overfishing, coastal development, and coral bleaching, ecosystems have been degraded to a minimum. mounds of dead coral covered with algae in murky waters "(Jackson, JBC, 1997, 2008).
The oceans are large dumps for urban and industrial discharges, oil spills (oil spills), fertilizers, insecticides or chemicals (more than half a million different substances), radioactivity, heavy metals etc. (Annual Report of the American Association for Progress of Science, 2008).
According to the latest report from the organization Worl Dwatch Institute; "The Situation of the World in 2003", it is estimated that between six and ten million tons of hydrocarbons end up in the sea a year, and 10 percent of them come from damaged tankers. Two million tons of waste are dumped into rivers, lakes, streams and the coast every day in the world. One liter of waste water contaminates about eight liters of fresh water.
Toxic pollutants, such as pesticides, are likely to be one of the most serious threats to Marine Biological Diversity and human well-being in the 21st century. But water pollution is not only related to chemicals. High concentrations of sediments frequently derived from the removal of vegetation cover in the catchment areas are equally damaging to marine species.
Fig. 3. Map of possible policies corresponding to "tipping" elements in the climate system and the density cover of the world population. Indicated subsystems could represent the threshold type of behavior in response to anthropogenic forcing of the climate, in which a small disturbance at a critical point qualitatively alters the future fate of the system (Lenton T.M., et. Al. 2008).
A worst-case warming of the Greenland ice sheet by more than three Celsius could cause the ice sheet to tend to disappear within 300 years. This would translate into a rise in sea level of up to seven meters. Arctic sea ice - as a sea ice melts, it reveals a much darker surface of the oceans, absorbing more radiation than the blank sea ice sheet so that warming is amplified.
In an article published in the journal Nature Geoscience (Carlson AE, et al., 2008), the melting of Greenland, the second world reserve of continental ice on the planet after Antarctica, could be occurring at a much higher speed than what it was thought. Worse, scientists seem to have so far underestimated the consequences of this thaw in their predictions. Especially those that refer to the increase in the level of the oceans that would be, according to the new data, much higher than expected.
The study combines computer models with extensive marine and land-based data on how quickly these ice masses melted in the past and how they caused sea levels to rise in an increasingly hot world. The authors have been able to draw conclusions from the disappearance of the so-called "Laurentis cap", the great mass of ice that 20,000 years ago covered a large part of the Earth's northern hemisphere. This huge platform, which covered a large part of what is now Canada and the United States, began to melt about ten thousand years ago, in response to an increase in solar radiation in the northern hemisphere of the planet, caused by the cyclical change that the orientation of the earth's axis undergoes.
The melting process accelerated especially in two periods (one 9,000 years ago and another 7,600 years ago), which caused a rise in sea level of 1.27 centimeters a year. These two periods of accelerated thaw, according to the study published in "Nature", happened precisely at a time when the temperature in summer was similar to that expected in Greenland for the end of this century.
Data from the Intergovernmental Panel for Climate Change (IPCC) suggest a rise in sea level between 2.5 and 10 centimeters over the next hundred years. But these estimates, according to Carlson et al., Are based on very limited data, much of it from the last decade. According to the new study, the actual rise in the level of the oceans for the next century will be between 30 and 60 centimeters, which will directly affect the lives of the hundreds of millions of people who live in coastal areas.
Icefall as a result of climate change is decimating biodiversity in shallow waters of Antarctica (Smale et al., 2008). This increase in the alteration of icebergs and their influence on the seabed, where 80 percent of Antarctic life occurs, could have serious consequences for animals such as Antarctic worms, sea spiders and urchins, at a depth of about 500 meters. According to the study, the release of the ice is closely related to the duration of what they qualify as winter sea ice. In addition, that ice has dramatically decreased in both space and time throughout the region during the last decades due to climate change.
In the journal "Proceedings of the National Academy of Science" (Lenton T.M et al., 2008) describes where small climatic changes can have large long-term consequences on ecological systems and human beings. Society can be placed in a false sense of security by a good projection of global change. The researchers of this publication describe that changes in the world can appear in a slow and gradual process on human scales. However, in some regions, forced by anthropogenic influences, the climate system could initiate abrupt and potentially irreversible changes (Fig. 3).
For defined subsystems of the earth system, the researchers introduce the term "tipping element". These overturning elements are rated as the most relevant for policy and require international consideration of the climate in politics. These are the critical elements noted.
Lenton's article also demonstrates how, in principle, early warning systems could be established through real-time monitoring and modeling, to detect the proximity of certain limit points. Sea ice from the Arctic and Greenland ice sheet are considered the most sensitive tipping elements with the least uncertainty.
Scientists hope that the ice cover from global warming will thin. The West Antarctic Ice Sheet is probably less sensitive as a rollover feature, but projections of its future behavior are highly uncertain. This also applies to the Amazon rainforest and boreal forests, the El Niño phenomenon, and the West African monsoon.
According to the 2007 UNDP report, the Atlantic thermohaline circulation as an archetypal deposit element, could undergo a major abrupt transition with a maximum of ten percent probability within this century.
In the government's Stern report (Stern Review: The Economics of Climate Change, 2006) on the economics of climate change, between 7 million and 300 million people would be affected by coastal flooding each year, there would be a reduction of between 30 and 50% in water availability in southern Africa and the Mediterranean, agricultural harvests would decline between 15 and 35% in Africa and between 20 and 50% of animal and plant species would face extinction.
Fig. 4. Industrial areas and seasonal deoxygenated waters (UNEP, 2004). Human action kills two hundred regions on the coast. The ‘deserts’ without oxygen are already double the number recorded in 1990.
In the UK, the most significant impact would be rising sea levels and flooding. Climatologists also predict that there would be an increase in events with heavy rainfall in winter and drier summers.
We share the same boat; And although the island countries and the impoverished populations that survive in the lowlands of the planet and in the coastal areas will most likely be the most affected, there is already the conviction that the negative consequences of climate change will end up affecting us all.
The main conclusion of the Stern Report is that the benefits that would be achieved with the urgent adoption of pertinent and firm measures could far exceed the economic costs of inaction and inaction. Using the results of formal economic models, the report has calculated that, if inactive, the total cost and risk of climate change will amount, henceforth, to a loss of a minimum of 5 percent per year of global GDP. Taking into account a broader range of risks and consequences, estimates of the damage that would occur could rise to a minimum of 20 percent of GDP "(ie, they could be multiplied by 4). However, the report suggests that: "... the cost of taking action - in particular reducing greenhouse gas emissions to avoid the worst consequences of climate change - can be limited to about one percent of Global GDP in each year ".
"The investment (one percent of GDP) made in the next 10 to 20 years will have a profound impact on the climate during the second part of this century, as well as in the century to come. Our current actions and those of the next decades, they could create the risk of a major disruption of economic and social activities, the scale of which would be comparable to the great wars and economic depression of the first half of the 20th century. These changes will be difficult and even impossible to remedy. "
The extinction of polar bears towards the end of the 20th century due to the reduction of the frozen layer in the Arctic is one of the possible effects of global warming (Epstein P. & Mills E., 2005).
Nineteen polar bear populations live on the Arctic coasts and islands of the five countries that surround the North Pole: the United States (Alaska), Canada, Denmark (Greenland), Norway, and Russia. Although they are large areas of territory, the truth is that their habitat is increasingly reduced. Global warming is especially affecting the poles, and recent studies claim that the Arctic could run out of ice in 2030 or even earlier. IUCN experts say that without permanent ice, polar bears will face serious difficulties in the future, as they depend on this sea ice to live, hunt and breed.
For its part, from the United Nations Environment Program (UNEP) they explain that delayed frost causes polar bears to lose critical fat reserves, which affects reproduction and the ability of pregnant females to produce enough milk for your puppies. Scientists have already recorded a 15 percent drop in the birth rate. Thus, the scarcity of food and the reduction of their habitat could be causing extreme behaviors in some specimens of this species. For example, a study published in the journal Polar Biology detected cannibalistic practices in northern Alaska and Canada, an extremely rare event, according to those responsible (Amstrup et al., 2006).
Likewise, pollution is another serious threat to polar bears. A report from the World Wide Fund for Nature (WWF) claimed in 2004 that these animals are being affected by toxic chemicals such as PCBs (polychlorinated biphenyls) and pesticides that would have been carried by winds and currents from countries south of the Arctic. The report also spoke of altered hormone levels, which could lead to reproductive problems and behavioral changes.
Average temperatures in the Arctic have risen by nearly 1.1 degrees Celsius in the last century, twice the global average, and winter temperatures are now 2 degrees Celsius higher, the report indicates (Stern et al., 2007). . In some parts of Alaska and Russia, there have been very strong increases in winter temperature, between 2 and 4 degrees Celsius, in the last half century, and the volume of ocean occupied by ice in the last three years has been the smallest since there are records.
Analyzes of data taken by satellites in the last 25 years show that there is an upward trend in maximum wind speeds in the strongest cyclones that originate in tropical seas, where the temperature of the sea water is higher. elevated. This pattern in cyclones, hurricanes or typhoons is directly linked to temperature "(Elsner J.B. et al., 2008).
For each degree Celsius rise in temperature of the sea's surface water, the frequency of the strongest hurricanes increases by a ratio of 13 to 17, which amounts to a 31% increase, points out the Nature article. The stronger the cyclone, the greater the increase in its strength ", say the authors of the analysis. According to their thesis, the engine of hurricanes is the temperature of the sea: the more it increases, the faster the hurricane spins around on its own. same counterclockwise (in the Northern Hemisphere) at speeds of between 150 and 240 kilometers per hour, records that define hurricanes.
Carbon dioxide (CO2) emissions are not only causing climate change, but also acidification of the oceans, as more and more scientific studies show. This problem causes the decline of very sensitive species, such as corals, mollusks or starfish, and could in turn have negative consequences for other species, and even increase global warming.
A recent publication by Jason Hall-Spencer on the Italian island of Ischia, whose seabed receives two million liters of CO2 per day due to volcanic escapes, describes that acidification has radically altered the ecology of the place, accounting for 30% less of species. Calcareous algae are among the most striking absences. It must be taken into account that with normal levels of pH the water usually covers 60% of the seabed (Hall-Spencer J.H. et al, 2008).
The scientists in that paper believe that all oceans by 2100 will have similar amounts of CO2 if emissions of this greenhouse gas continue to increase.
Likewise, researchers have detected the scarcity of other species with a calcareous skeleton, such as corals, stars or sea urchins. The lack of the latter, for example, can be a serious problem in the Mediterranean, as it is a natural predator of the Culerpa, an invasive toxic algae in this sea that has wiped out many native species.
For their part, Jon Havenhand and Michael Thorndyke have overturned the belief that the chemical balance of the sea is immovable. Their work, published in the journal Current Biology, states that the pH of sea surface water has decreased by as much as 25% since the beginning of industrialization. This increase in acidity, these experts assure, threatens the viability of many marine species (Havenhand J. & Thorndyke M., 2008).
Various studies, such as those already cited, show that the acidification process prevents corals from manufacturing the calcium carbonate that forms their framework, and inhibits the transformation of the calcium necessary for the cell covers or skeletons of mollusks, calcareous plankton, oysters, clams or mussels.
In addition to calcification, acidification could cause various direct negative effects on the physiology and reproduction of living beings, such as hypercapnia (excessive presence of CO2 in body fluids). Other consequences could be more indirect, but no less worrying, such as the decline in food resources or the destruction of the habitat of certain species, such as those that live on coral reefs.
In any case, scientists recall that once the ocean's pH has dropped, it will take thousands of years to reverse the change, even if steps are taken to reduce CO2 emissions. Therefore, some experts recommend preparing for possible negative impacts that may affect, for example, fisheries.
The European Network of Excellence for Ocean Ecosystem Analysis (EUR-OCEANS - http://www.eur-oceans.eu) recalls that the colder and more acidic southern and Arctic oceans could become totally inhospitable at the end of this century for this type of organisms. This phenomenon, together with the excess of nutrients (mostly nitrogen), caused by the dumping of agricultural fertilizers and waste, contributes to the increase in seas and oceans of the so-called "dead zones". Here, the low oxygen levels put extreme living conditions for the vast majority of marine species.
The "Dead Zones", which are areas where oxygen is severely scarce, are reaching alarming proportions and are spreading across the world's seas and may become an even greater danger than overfishing (Fig. 4.).
At the beginning the degradation of the waters in the oceans was slow and silent. But currently the magnitude reached is alarming.
Researcher Robert J. Díaz, from the Virginia Institute of Marine Science and one of the world's leading authorities on the phenomenon, estimates that there are currently 405 dead zones in the world (Diaz R.J. & Rosenberg R. 2008). In his previous count - from about five years ago, which is the one seen in the graph - they were close to 150. His calculations coincide with those of the United Nations, which has warned of the "rapid increase in these areas." .
Fig. 5 .: The number of Dead Zones has increased by a third between 1995 and 2007, and it is expected that in the future it will grow more, as a consequence of climate change (Source: Diaz R.J. 2008).
Most are periodic dead zones. They coincide with the arrival of the rains after the summer. El agua recoge los excedentes de nutrientes de los campos de cereales, profusamente abonados en los países ricos. En los deltas y las desembocaduras, si las corrientes no los dispersan, ponen en marcha el proceso.
La relación con el desarrollo está clara. Desde los años sesenta del siglo XX, el número de zonas muertas identificadas se duplica cada década: 10, en 1960; 19, en 1970; 37, en 1980; 68, en 1990. Y su reparto -casi todas en el hemisferio norte- confirma su vínculo con prácticas de agricultura intensiva (Fig.5).
Approximately 90 percent of international trade is transported by sea. More than 29 percent of the world's oil production comes from the oceans. Beach tourism and cruise ships are an important source of income for many countries, especially small island developing states. Every year almost 130 million tonnes of fish are caught worldwide, with an approximate value of 60 billion dollars, and the fisheries sector and aquaculture alone employ 150 million people.
Además los océanos a través de sus interacciones con la atmósfera, litósfera y la biósfera, juegan un papel relevante en la conformación de las condiciones que hacen posible las distintas formas de vida del planeta. In fact, without the oceans, life would not exist on our planet.
¿Cómo se relacionan las cadenas tróficas cerca de las costas (Fig. 6.)? ¿Cómo se ven afectadas por las actividades humanas? ¿Es posible evaluar numéricamente los impactos que ocasionamos a nuestros recursos naturales costeros? El artículo publicado en la revista Marine Ecology Progress Series por Vera Vasas y colaboradores (2007) enfoca algunas de estas interrogantes utilizando análisis cualitativo de la red estructural del ecosistema. Se analiza principalmente el papel de las especies capaces de formar florecimientos de algas y de mareas rojas, así como el papel de las medusas en sistemas eutroficados. De igual manera se analiza la contribución de las influencias humanas en las cadenas alimenticias: descargas de nutrientes y el efecto de la sobrepesca.
Fig. 6. Cadena Trófica: en los primeros eslabones de esa cadena los microorganismos fabrican sus propios alimentos y luego son comidos por otros organismos, mayores, que a su vez serán comidos por otros (Sommer M., 2005).
A pesar de su importancia crítica, suele considerarse que los ecosistemas oceánicos carecen de utilidad en el Mundo. La ignorancia generalizada sobre su importancia ha contribuido a este concepto y ha promovido la destrucción y degradación de los ecosistemas (Report of the Pew Oceans Commission, 2003, Reporte de la Comisión Americana de los Océanos, 2003).
En el Mundo se ha descuidado gravemente la conservación de la Diversidad Biológica de los océanos y hay ecosistemas enteros amenazados de extinción (Mar del Norte, Mar Báltico) (http://www.helcom.fi/helcom.html).
Dos tercios de la acuicultura dependen del ecosistema costero (manglares, pastizales, arrecifes coralinos etc). A medida que disminuye la extensión de los manglares, humedales costeros y praderas marinas, los hábitats costeros pierden su capacidad de actuar como filtros de organismos y sustancias contaminantes.
Los indicadores de perdida de hábitat, enfermedad, especies invasoras y blanqueamiento de corales (efecto invernadero) muestran todos que la biodiversidad esta disminuyendo. La sedimentación y la contaminación provenientes de la tierra están asfixiando algunos ecosistemas costeros, mientras que en ciertas áreas la pesca de arrastre esta reduciendo la diversidad. Algunas especies comerciales como el bacalao del Atlántico, cinco clases de atún y abadejo se hallan amenazados en todo el mundo, junto con varias especies de ballenas, focas, tiburones y tortugas marinas. Más de la mitad de los arrecifes de coral del mundo están potencialmente amenazados por las actividades humanas, y en las zonas más pobladas, esa proporción asciende al 80 por ciento, al mismo, cerca de 27 por ciento se perdieron.
Entre los grandes desafíos del siglo XXI la sociedad tiene que aprender que los Océanos son fuente de vida como también puede serlo de muerte. The oceans must, therefore, be appreciated and protected; and if the ecological needs of ocean ecosystems are relegated to oblivion; the state of the marine environment will become an impediment to sustainable development rather than a resource for it.
The world should rethink the way economic growth is being measured. Durante mucho tiempo las prioridades de desarrollo se han centrado en lo que la humanidad puede extraer de los ecosistemas, sin pensar demasiado sobre como afecta esto la base biológica de nuestras vidas. Se puede decir que ha habido un progreso muy limitado en la reducción de la pobreza en los países en desarrollo, y la Globalización, por si misma, no ha beneficiado a la mayoría de la población mundial. En general, los intentos por impulsar el desarrollo humano y para detener la degradación del medio oceánico, no han sido eficaces durante la pasada década. Los escasos recursos, la falta de voluntad política, un acercamiento no coordinado, y los continuos modelos derrochadores de producción y de consumo han frustrado los esfuerzos de poner en ejecución el desarrollo oceánico sostenible, o el desarrollo equilibrado entre las necesidades económicas y sociales de la población, y la capacidad de los recursos oceánicos y de los ecosistemas para resolver necesidades presentes y futuras.
La responsabilidad de proteger los océanos recae no sólo sobre los políticos quienes definen las condiciones nacionales e internacionales de protección de los ecosistemas, sino también es tarea de cada individuo. La exigencia a los políticos para que tomen medidas más efectivas frente a esta problemática debe estar acompañada del compromiso de cada uno de nosotros por actuar en una forma más responsable en la promoción de la defensa de las metas por la protección de los océanos.
Oceanógrafos Sin Fronteras pide, además de fondos, medidas políticas: crear reservas marinas, respetar la regulación sobre pesca, combatir los vertidos de fertilizantes, aplicar seriamente las medidas para reducir emisiones de gases y promover medidas de conservación a escala local, nacional e internacional. No parece haber otra receta para salvar los océanos (http://www.oceanografossinfronteras.org).
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