John A. Hargreaves
World Aquaculture - Editor in Chief
John A. Hargreaves | Sunday, September 15, 2019
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