The IPCC summarized the recently released Climate and Land Report with a tweet that said “Land is under growing human pressure. Land is a part of the solution. But land can’t do it all.” The report describes how the changing climate is degrading the capacity of land to grow food, already exacerbated by poor land-use practices in some areas. The urgency to act is reinforced by the need to limit warming this century to 1.5 C to avoid effects that are increasingly being described using terms like “crisis” or “emergency.” To avoid the 1.5 C temperature change, greenhouse gas emissions would have to be reduced to zero by mid-century.

We live in the Anthropocene and the IPCC estimates that humans are using or have impacted more than 70 percent of the global ice-free land surface. Converting forests and other natural areas into pasture or cropland is a major source of emissions. Although land currently absorbs 30 percent of global emissions and absorbs more carbon that it emits, ongoing deforestation and land degradation threaten the capacity of land to be a sink for emissions.

About 1/4 of greenhouse gas emissions come from agriculture, deforestation and other land uses, 3/4 comes from other human activities, primarily transportation, power production and heavy industry. If broader value-chains are considered, the global food system accounts for more than 1/3 of emissions. Agriculture is a major emitter of methane, a gas with a more potent greenhouse effect than CO2. Methane emissions from agriculture have been increasing in response to expansion in the number of ruminant livestock and the area dedicated to farming rice.

The effects of climate change on land are already being felt. Over the last five decades, the air over land is warming at a rate twice as fast as for the planet as a whole. Heat waves, droughts and wildfires are now more common, as are extreme weather events, flooding and soil erosion. The yields of crops grown in tropical zones are declining, threatening food security and livelihoods, increasing migration and the potential for conflict.

Only 10 percent of the global ice-free land surface is involved in crop production, along with 2 percent in irrigated crop production. This is the land that is critical for human food production, especially commodity grains, but it is also the land critical for fed aquaculture. In recent decades, about 10 percent of grain production has been lost to drought, flooding and extreme weather. Yields of the major grains — corn, wheat, soybean and rice — are expected to decrease, resulting in an increase in grain prices of 7.6 percent by 2050. The nutritional quality of these grains is expected to decline, threatening food security.

To limit global heating to less than 1.5 C, the report provides a menu of options to reduce emissions or enhance carbon sequestration by land. Obviously stopping deforestation and protecting the remaining forests is a key part of any broad-based set of solutions. A more sustainable agriculture is another key solution. Farming methods such as reduced tillage and other better farming practices can conserve soil carbon. Using less fertilizer can reduce nitrous oxide emissions. Changing feed composition for livestock can reduce methane emissions. Here is a specific example where aquaculture may provide a direct contribution. Livestock diets that include an extract of the red seaweed Asparagopsis result in 24-48 percent lower methane emissions. A new company, Greener Grazing, aims to produce this seaweed at commercial scale.

Another solution proposed in the report, one receiving disproportionate attention from the press, is for people to change their diets towards those with lower impact, usually interpreted to mean less meat. The report also calls for reducing food waste, which currently accounts for 25-30 percent of food produced.

So, what are the implications of this IPCC report for aquaculture, particularly inland aquaculture? Perhaps most concerning is the effect of global heating on the availability of fresh surface water for inland aquaculture. The report predicts that the land area with water stress will expand, forcing prioritization of water use in those areas for direct human needs. Also concerning is the effect on the supply of grains and their by-products for use in aquafeeds. Ultimately the sustainability of fed aquaculture is tied intimately to the sustainability of crop production. According to the FAO, the farming of fed species has increased by 10 percentage points from 2000-2016 to 69.5 percent. Finally, although aquaculture makes a miniscule contribution to greenhouse gas emissions, aquaculture ponds are sources of methane, at a magnitude similar to that from ricefields.

The young Swedish activist, Greta Thunberg, was inspired to commit acts of civil disobedience by a climate change nightmare. She recently admonished members of the US Congress in saying “I know you are trying but just not hard enough.” It’s a message for all of us to try harder, to do what we can, to play our part in providing solutions that can get us on a path towards a sustainable future. Although aquaculture is still rather small relative to agriculture as a whole, there is always room for improvement.

A number of reports in recent years have demonstrated that the environmental impacts of animal protein production are not equal and that fish production is one of the most efficient forms. Aquaculture has many great stories to tell, stories that can be used to inform a food production policy agenda that favors efficient forms of animal protein production like aquaculture.

In the very near future, the IPCC will release another special report on the ocean and cryosphere. The report is expected to discuss the likely displacement of millions of people caused by rising sea levels. Obviously vast areas of coastal aquaculture ponds would disappear in the inundation. Ocean acidification, superstorms and marine heatwaves are likely to prevent the full realization of aquaculture’s potential in marine waters. The time to prepare is now.
— John A. Hargreaves, Editor-in-Chief