Mussel Farming Environmental Impact
Water use for animal protein production is a major challenge for humanity. Only 2.5% of all water on Earth is freshwater. Of this, about 69% is frozen as snow and ice, and more than 33% is stored in groundwater. This means that only 0.3% of all the freshwater on Earth is readily available as surface water in lakes, swamps, rivers and streams.
Freshwater resources are not evenly distributed. More than 2.3 billion people in 21 countries live in water-stressed basins; 1.7 billion live under conditions of water scarcity; and a billion people do not have sufficient access to clean water. By 2055, 64% of the world’s population will be living in water-stressed basins and 33% in areas of absolute water scarcity.
Livestock production demands large volumes of freshwater and it is estimated that livestock industries consume 8% of the global water supply, with most of that water being used for intensive, feed-based production.
Marine aquaculture is the food-producing sector least dependent on freshwater availability, however, feed resources used in marine aquaculture contain agriculture compounds, which results in a freshwater footprint and heavy dependence on freshwater and land for the provision of feeds. It is the efficient use of feed that determines the efficiency of fed species and this should be the focus of improving the environmental performance of all such species.
Like other filter feeding molluscs that currently account for 58% of marine and brackish water animal aquaculture production, mussels offer an advantage over all other animal protein sources, as no freshwater is used in the farming process or in previous stages of the production chain. Marine filter feeders such as mussels are vegetarian that feed at the base of the food chain, up taking their food from the plankton available in the sea, with no added feed.
The three components of a mussel’s diet are detritus, bacteria and phytoplankton and they selectively enrich the organic content of ingested matter by rejecting particles of higher inorganic content before ingestion. Being at a low trophic level means they have a minimal amount of mercury, in comparison to large predator fish such as tuna and swordfish from capture fisheries.
There seems to be a large overlap of resources between the aquaculture, livestock and poultry sectors; soybean and maize constitute the main food crops of importance for marine aquaculture.
Some terrestrially derived feed ingredients that are considered viable replacements for fishmeal in feed, such as gluten from wheat and maize, are very energy intensive, whereas others such as sunflower also have a strong water footprint and there are major concerns regarding production of soy and palm oil in relation to habitat loss.
These authors consider that the amount of crop resources used for marine aquaculture will probably increase in the future as (i) overall aquaculture production will increase; (ii) the share of aquaculture production using commercial pelleted feeds will increase and (iii) the availability of fish protein resources will be limited (stable or declining fish stocks, insufficient fish processing wastes).
Mariculture can only become as successful as agriculture in the coming century if carnivores can be produced at around Trophic Level 2, based mainly on plant resources. There is little potential for increasing the traditional fishmeal food chain in aquaculture.
Land is a limited resource that provides food, fiber, shelter and important ecosystem services to humanity. Pasture area is projected to increase by about 1.6 million km2 until 2050. A review of the land used for edible animal protein provided by Flachowsky et al. found that there are large differences between animal species/categories and their potential to produce edible protein depending on many influencing variables.
Reviewing Life Cycle Assessment (LCA) studies De Vries and de Boer found that the production of 1 kg of beef or 1 kg of edible beef protein required the most land and had the highest global warming potential followed by the production of 1 kg of pork, chicken, eggs and milk. In the future, there will be strong competition for arable land and non-renewable resources, water, feed, food, as well as between areas for settlements and natural protected areas.
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