Global Warming Reduction by Switching to Healthy Diets

by Shelby Long

The consumption of food and beverages accounts for 22–31% of total private consumption greenhouse gas (GHG) emissions in the EU (Tukker et al. 2009). More specifically, the production of meat and dairy products tend to produce greater GHG emissions (Audsley et al. 2009). Saxe et al. (2012) examine how different diets, which are composed of different foods, are associated with varying potential GHG emissions. They use consequential Life Cycle Assessment to compare the emissions, or global warming potential (GWP), from food production for an Average Danish Diet (ADD), the Nordic Nutritional Recommendations (NNR), and a New Nordic Diet (NND), which was developed by the OPUS Project. They determined that the GHG emissions association with NNR and NND were lower than those associated with ADD, by 8% and 7%, respectively. When taking into account the transport of food, NND emissions are 12% less than ADD emissions. With regard to organic versus conventional food production, GHG emissions are 6% less for NND than for the ADD. Saxe et al. adjusted NND to include less beef and more organic produce, and they substituted meat with legumes, dairy products, and eggs, which made the diet more climate-friendly. As a result of this adjustment, the GHG emissions associated with NDD was 27% less than emissions for ADD. Continue reading

The Effect of Climate Change on Prawn Fishing in Bangladesh

by Shelby Long

Nearly 400,000 Bangladeshi people are financially dependent on the fresh water prawn market. Bangladesh offers the natural resources and ideal climate to support prawn farming from wild postlarvae. In 2002, a ban was placed on the fishing of wild postlarvae by the Department of Fisheries in Bangladesh. However, this ban is not strongly enforced, so many locals who rely on the market to make a living continue to fish. Ahmed et al. (2013) examines the effect of climate change on prawn fishing in the Pasur River through variables, including cyclones, salinity, sea level rise, water temperature, flood, rainfall, and drought. The Pasur River ecosystem, more specifically the prawn postlarvae, is highly vulnerable to climate changes because it is only one meter above sea level. Researchers surveyed and interviewed local fishermen, government fisheries officers, policymakers, and non-governmental organization workers. They also conducted focus group discussions with fishers and local community members regarding the various climate-affected variables under study. Ahmed et al. determined that prawn postlarvae catch has gradually decreased by approximately 15% over the past five years, with cyclones being the most significant climatic variable affecting the catch. Decreases in postlarvae prawn catch impact the health and socioeconomic well-being of local fishermen, many of which are women and children. Continue reading

Implications for Disease Control in Aquacul-ture

With over-exploitation of coastal fisheries and rising disease rates of ocean populations, fish abundance levels have been dramatically decreasing. The outbreak, persistence, and eradication of infectious diseases are often dependent on the density of the host population. The growth of aquaculture has produced a large density of fish in fish farms, making them more susceptible to disease. They are often open to the surrounding ecosystem and therefore are exposed to wild fish populations as well. Krkošek (2010) explores the connection between outbreaks of parasites in wild salmon and density threshold in aquaculture growth. High densities lead to higher transmission rates of infectious diseases because of increased contact with infected individuals. Wild-farmed populations can exceed host density threshold from an influx of migrating individuals, increases in aquaculture production, or environmental changes such as global warming. In contrast, populations with lower densities show a much lower rate of susceptibility and slower rate of disease spread. Fisheries reduce abundance levels of wild populations, which should lead to a decrease in disease and parasite abundance as well. However when a predatory population declines, the prey population increases and therefore increases susceptibility of disease. —Lauren Lambert
Krkošek, M., 2010. Host density thresholds and disease control for fisheries and aquaculture. Aquaculture Environmental Interactions 1: 21–32.

Industrial aquaculture and number of fish farms are growing. They often have larger domesticated abundance than wild populations. These domesticated populations are concentrated by pens, nets, cages, rafts, or ropes that are open to the surrounding areas. Therefore any disease or parasites that arise in these populations will be open to the surrounding ecosystem and can be transmitted to wild populations. This is a major challenge for the aquaculture industry because of the concern for conservation of the wild marine ecosystem. The most common measure of disease persistence is known as R0, or the net reproductive value. If R0 >1, the parasite population can invade host population. If R0 <1, infections do not replace themselves and parasite populations will eventually die out. This is the process of disease eradication. Populations are susceptible to microparasites such as viruses, bacteria, and protists. Dynamics of microparasite diseases can be modeled by dividing host populations into categories determining status of infection (susceptible, infected, recovered). Individuals become infected by being exposed to others that are infected. Even if an individual recovers, over time it becomes more susceptible to disease and could become infected again. The number of infected individuals generated by a single individual can be determined by multiplying the average duration of infection period by the rate at which hosts become infected.
Macroparasites include helminths and arthropods such as intestinal worms and ectoparasitic copepods. Unlike microparasites, these must leave the initial host in order to complete their life cycle. They also produce sexually in or on a host. For example, sea lice reproduce on the surface tissue of fish. Models describing macroparasites must track free-living stages as well as number of parasites per host, per population. Birth and death rates, rate of infection of hosts, and host/parasite mortality rates are also determined.
Theory predicts that host density thresholds are important for host-parasite dynamics. For example, increases in sea lice in salmon were associated with small incremental changes. This is consistent with the theory in which a small increase in host density that crosses threshold triggers a sudden outbreak of disease. Threshold capacity could have been decreased by environmental conditions such as temperature, leading to an acceleration of an epidemic. Vaccination has contributed to the eradication of diseases in fish farms despite the large increase in fish production. Most developments of vaccines can only treat bacterial and viral diseases, and not parasitic ones.
Spatial scale of thresholds is dependent on physical characteristics that influence dispersion and survival of free-living parasites and infectious agents. Pathogens existing in marine environments are long lived and widely dispersed compared to those on land because they are able to be transported over long distances in a more stable condition of temperature and moisture. This is especially true in the case of wild marine populations that have hosts that are highly mobile or migratory which leads to spread of infection at a much more rapid rate. Outbreaks have been shown to follow the direction of currents, predicted using hydrodynamic modeling. With these migratory fish spreading disease to other populations, epidemics in fish farms can be spread over very large scales. However the infection is likely to decline with increased distance from the source population.
Parasitic life cycles are influenced by a variation of environmental factors such as temperature, moisture, and salinity. Global climate change can have a profound influence on these parameters. Developmental rates of parasites are highly dependent on the consistency of temperature. Knowledge of disease outbreaks and its possible influences has important implications for coastal fish farm planning. Minimizing transmission of pathogens among farm fish to wild hosts could increase the size of wild populations. This can be done by placing farms further away from wild fish migration routes and in locations that have low ocean tides and currents, to minimize rates of disease spreading. Selective breeding of fish that are resistant to disease can also provide the future populations with a higher survival rate. Increased vaccinations of fish, increased circulation of facilities, and maintaining lower density levels in these fish farms provides advances in disease control.

Effects of Fish-Farms on Marine Biodiversity Along the Mediterra-nean Coast

The expansion and growth of offshore mariculture is a growing business. The environmental effects of this industry are of particular concern because of the impacts they have on marine habitats and biodiversity<!–[if supportFields]>XE “biodiversity”<![endif]–><!–[if supportFields]><![endif]–>. Mirto et al. (2010) investigated the effects that fish farms have on the metazoan meiofaunal communities existing in areas exposed to fish farms along the coast of the Mediterranean Sea. The potential effects of fish farm effluents on the abundance and community composition of meiofauna were analyzed by comparing two different habitats in four different regions with different background trophic<!–[if supportFields]> XE “trophic” <![endif]–><!–[if supportFields]><![endif]–> conditions. It was found that there are conflicts between aquaculture<!–[if supportFields]> XE “aquaculture” <![endif]–><!–[if supportFields]><![endif]–> and the conservation of marine habitats and benthic primary producers. The organic enrichment of sediments falls beneath the sea cages used by fish farms. This sedimentation of particulate waste products from the fish farm has a direct effect on the local habitat. The continuous deposition of feces and food pellets from fish cages can alter the quantity as well as biochemical composition of sediment organic matter. The extent to which these areas are affected differs in different regions/habitats. Investigating meiofaunal assemblages in different regions of the Mediterranean Sea identifies the changes that are caused by aquaculture on benthic ecosystems and can provide insight to what is going on in these marine communities. —Lauren Lambert
 Mirto, S., Silvia B., Cristina G., Maja K., Antonio P., Mariaspina S., Marianne H., and Perry R.I., Ommer RE., Barange M., Werner F. 2010. The challenge of adapting marine social-ecological systems to the additional stress of climate change. Current Opinion in Environmental Sustainability 2,  356–363.

Mirto et al. (2010) hypothesized that fish farms influence the meiofaunal assemblages of existing habitats. This includes abundance, community structure, and diversity. Four regions along the Mediterranean Coastal zones were selected in order to provide a variety of different environmental conditions. Two different habitats were selected, meadows of seagrass vs. soft non-vegetated bottoms. Control sites were also chosen to match conditions and environmental features found at the bottom of fish farm cages. These sites were located at a distance of at least 1000m upstream from the fish farms to be certain that this habitat would not be affected. The sediment protein, carbohydrate, and lipid contentents were determined. The amount of meiofauna was determined by sieving through 1000 mm sieve for macrobenthos and macroalgae, and 32 mm sieve to retain smaller meiofauna. The differences between control and impact sediments were calculated using three-way-analysis-of-variance (ANOVA<!–[if supportFields]> XE “ANOVA”<![endif]–><!–[if supportFields]><![endif]–>). When significant differences were observed between the two groups, a post-hoc Student-Newman-Kuels test (SNK) was also used to assess this information.
The observations of the study showed differences between impacted and control sites as well as in the four geographical areas. SNK tests revealed a consistent increase in biopolymeric C concentrations in farm-impacted vegetated sediments in Cyprus, both habitats in Greece, and in non-vegetated sediments in Italy. Protein to carbohydrate ratio increased in both habitats in Italy and non-vegetated sediments in Spain. A decrease in impact sediments was observed in both habitats of Greece. The SNK test indicated a significant increase of meiofaunal abundance in impacted sites with vegetated sediments in Cyprus, in non-vegetated sediments in Italy, but no difference between control groups in other regions. In summary, Mirto et al. found that the differences between control and sites impacted by fish farms varied depending on the region.
Differences between impact and control sites in the meiofaunal community composition were only significant in non-vegetated sediments in Cyprus or Greece. Nematodes and Copepods were the most dominant taxa followed by polychaetes, ostracods, turbellarians, oligochaetes, gastrotrichs, and all other taxa. The richness of meiofaunal taxa decreased significantly in impacted sites in non-vegetated sediments but no significant differences between impact and control sites were observed in sea grass sediments. The taxa that disappeared beneath the cages varied throughout the sites, but always compromised the rare taxa which make up  <1% of total meiofaunal abundance.
Fish farms typically have an effect on the attributes of the benthic environment beneath cages and show a significant amount of modifications in the abundance, biomass, species composition, and evenness of meio and macrofauna.  However these observed changes associated with the presence of fish farm effluents are often not consistent because meiofaunal abundance may increase or decrease beneath the cage depending on characteristics of the site or farm. The abundance of meiofauna was generally higher in fish farm sediments, which could be a result of limited organic enrichment in the sediments beneath the cages. There is a clear and consistent meiofaunal response to the fish farm deposition in sea grass sediments. Posidonia oceanica<!–[if supportFields]> XE “Posidonia oceanica” <![endif]–><!–[if supportFields]><![endif]–> is the sea grass existing on the sites that plays a key ecological role for many of the organisms and assemblages by preserving biodiversity<!–[if supportFields]>XE “biodiversity”<![endif]–><!–[if supportFields]><![endif]–>. It is difficult to detect effects of fish farm biodeposition on sea grass meadows because the grass masks the changes in organic composition. The presence of a large number of filter feeders and detritus feeders within sea grass beds can also act as a buffer for the organic enrichment because of the amount of biodeposits that they consume.

Actual changes are difficult to know because of these supplemental factors. However in the long term, the increased sedimentation and waste particles that result from these farms does lead to the deterioration of the sea grass system and will eventually result in disruption of the ecosystem in place. Fish farm biodeposition in the Mediterranean Sea can provoke changes in meiofaunal abundance, community structure, and biodiversity<!–[if supportFields]> XE “biodiversity” <![endif]–><!–[if supportFields]><![endif]–>. Because of the amount of variation between the sites, it is important to use indicators of fish farm impact in vegetated and non-vegetated systems in the future. 

Are Fish Farms the Answer in Supplying Our Growing Population?

There is a great controversy surrounding production through fish farms as opposed to a reliance on wild fish sources. Wild fisheries populations are declining, however aquaculture<!–[if supportFields]> XE “aquaculture” <![endif]–><!–[if supportFields]><![endif]–> could become the most sustainable source for protein for humans. Currently there is a reliance on meat from livestock, and food consumption is increasing worldwide. The population is estimated to increase from an already high 6.9 billion to 9.3 billion people by 2050. With this in mind, the question arises about where global meat will come from. Raising livestock uses up a vast amount of land, freshwater, fossil fuels, and results in organic waste and fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–> run-off that has a negative impact on rivers and oceans. These same issues apply to fish farming and other aquaculture, which results in fish sewage, depletion of mangrove forest<!–[if supportFields]> XE “forest” <![endif]–><!–[if supportFields]><![endif]–> for shrimp growth, and densely packed salmon<!–[if supportFields]> XE “salmon” <![endif]–><!–[if supportFields]><![endif]–> farms that cause disease and parasites<!–[if supportFields]> XE “parasites” <![endif]–><!–[if supportFields]><![endif]–>, which kill off their populations and infect native species as well. Larger offshore pens are much cleaner and could serve as a place for expansion of aquaculture and could even become more sustainable than wild fish or raised beef. —Lauren Lambert
Simpson, S., 2010. The Blue Food Revolution. Scientific American 304, 54–61

Simpson (2011) addresses the benefits of aquaculture<!–[if supportFields]> XE “aquaculture” <![endif]–><!–[if supportFields]><![endif]–> and fish farming as a solution to the global food security issue. Coastal fish farms pollute the ocean with fish excrement and food scraps, particularly in the shallow waters. Offshore sites such as Kona Blue Water Farms have eliminated the pollution issue by submerging paddocks that are anchored in the presence of rapid currents that quickly dilute and sweep away the harmful waste before it can become a problem for marine ecosystems nearby. These paddocks are cone shape and made from solid material that is strong enough to keep sharks from getting into the fish supply. They contain massive amounts of domesticated yellowtail, which serve as an alternative to wild tuna. These fish are fed pellets of fishmeal and oil made from smaller fish. The yellowtail could survive on a purely vegetarian diet, but their meat would not contain the fatty acids and amino acids<!–[if supportFields]> XE “amino acids” <![endif]–><!–[if supportFields]><![endif]–> that produce a healthy, good tasting fish. Other farms raise seaweed and filter feeding animals such as mollusks near the fish pens to use up the waste. Cutting edge designs for fish pens are submerged, steered by large propellers, and ride on ocean currents to stimulate fish maturation. The pens would then return months later to the starting point or designated destination for delivery of fresh fish to market.
The fishmeal used to feed the fish farms is of concern because of the rapid decline of smaller fish species such as anchovy<!–[if supportFields]> XE “anchovy” <![endif]–><!–[if supportFields]><![endif]–>. Anchovy concentration in feed pellets were reduced from containing 80% in 2005 to 30% in 2008 by adding a higher concentration of soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> meal and chicken oil. However as the demand for fish farms increases, sardine and anchovy populations are in jeopardy of a decline in population size. Aquaculture is the fastest growing food production sector in the world, expanding at a rate of 7.5% per year since 1994. At this rate, fish and all of its products could be exhausted by 2040 and therefore, the main goal is to eliminate the use of wild fish from feed products altogether. One possible solution is to use docosahexaenoic acid (DHA) from microscopic algae because of the need to eliminate all agricultural resources from feed, and push towards a reliance on easily grown seaweed and zooplankton<!–[if supportFields]> XE “zooplankton” <![endif]–><!–[if supportFields]><![endif]–>.
The world health organization predicts a 25% increase in meat consumption by 2050. Simpson leans towards aquaculture<!–[if supportFields]> XE “aquaculture” <![endif]–><!–[if supportFields]><![endif]–> for the global protein supply. Cattle eat a large amount of heavily fertilized crops, and pig and chicken farms are extremely polluting to the environment. Raising Angus beef requires 4,400 times more high quality pastureland than seafloor needed for the equivalent weight of farmed Atlantic salmon<!–[if supportFields]> XE “salmon” <![endif]–><!–[if supportFields]><![endif]–>. However fish farms also have their flaws. Areas below coastal fish farms have huge dead zones, similar to the results of fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–> run-off from the Mississippi River into the Gulf of Mexico<!–[if supportFields]> XE “Gulf of Mexico” <![endif]–><!–[if supportFields]><![endif]–>, or harmful algal blooms from pig farms in the Chesapeake Bay. Although fish farms are relatively detrimental to ecosystems, marine ecosystems have the ability to recover in less than a decade, whereas a cattle farm would take centuries to overcome the damage.
Fish farming reduces the size of marine fishing fleets, so that although fuel consumption and emissions are higher on an offshore farm, they are not as high as would result from fleets catching equivalent amounts of wild fish. Aside from these advantages, inefficient and harmful fishing methods such as trawling and dredging kill millions of animals as bycatch, that are regarded as worthless and tossed aside. Fish farming is also more efficient in that the raised fish do not have to waste energy searching for food, avoiding predators, and reproducing. Most of their diet goes into growth, so they mature at a faster rate.

Fish farming already accounts for 47% of global seafood consumption, and could potentially rise to 62% of total protein supply by 2050. Although there are many benefits to this method of food production, society is not yet ready to switch to these measures. But Americans do not yet accept this transition to an increased reliance on aquaculture<!–[if supportFields]> XE “aquaculture” <![endif]–><!–[if supportFields]><![endif]–>; the public accepts domestication on land, but has a perception of the ocean as a wild frontier. Perhaps at some point this will change.