Each time farmers irrigate their wheat fields at the beginning
and end of a crop cycle, they wash thousands of tonnes of nitrogen
fertilizer into the Gulf of California, a body of water so rich in
biodiversity that celebrated ocean explorer Jacques Cousteau once
called it the "aquarium of the world." The farmers in the Yaqui
Valley are proud to have some of the highest wheat yields in the
world. But equally high are their fertilizer application rates:
some 250 kilograms of nitrogen per hectare, which is far beyond the
The wheat plants can only use a small fraction of this nitrogen.
Scientists estimate nearly two-thirds of the nitrogen applied in
fertilizer in the Yaqui Valley is lost in the atmosphere and runs
off into surface waters. Year after year, an estimated
11,000 to 22,000 tonnes of nitrogen are washed into the sea. This
triggers a particularly dramatic effect in the nitrogen-deficient
waters of the Gulf of California, stimulating algae blooms within
days of fertilisation and irrigation.
In 2005, a team of researchers from Stanford University in the
United States demonstrated the close correlation between overuse of
nitrogen fertilizer and explosive algae growth in coastal waters
(Beman et al., Nature 434:211) through satellite pictures. The
images show thick algae bloom right off the coast, fuelled by
nitrogen run-off from wheat fields.
The researcher measured algae blooms as big as
577 square kilometres in the Gulf of California, which is one of
the most productive and biologically diverse marine ecosystems in
the world. More species of whale and dolphin feed and breed here
than anywhere else. Nearly 900 fish species and 34 species of
marine mammals swim in these waters, and more than 800 of the
Gulf's species are found nowhere else. Hundreds of species of
birds, both migratory and resident, nest in mangroves and coastal
lagoons. The effects of the regular algae blooms on this unique
diversity are potentially significant
Algae blooms are not unique to Northern Mexico. They are
occurring with more frequency and in more locations worldwide than
ever before. Virtually every coast in the United States is now
affected by regular algae blooms. In China, the average number of
harmful blooms escalated within two decades, from less than 10 in
1980 to more than 80 in 2000. A recent European Environmental
Agency report found that runoff from agricultural activities is the
main source of nitrogen pollution, and that the accumulation of
nutrients ('eutrophication') is "still one of the major
environmental problems across Europe"
(www.eea.eu.int, Report No. 7/2005).
This threat could be easily avoided by reducing the overuse of
fertilizers and by farming more ecologically. A first and easily
implemented step would be precision fertilizing. Applying smaller
quantities of fertilizer at specific times in the crop cycle
directly on the plants would ensure most of the fertilizer was used
and not washed away. Farmers would save money while not
compromising yields and the environment would be less exposed to
harmful effects of nutrient overloading.
But farmers in the Yaqui Valley are reluctant to apply these
methods, be it that precision fertilizing is deemed too
complicated, or that they are too used to the high-input,
high-output methods of the so-called Green Revolution - a
revolution that started right here, in the heart of the Yaqui
Valley. In the 1940s, future Nobel Peace Prize winner Norman
Borlaug started a wheat breeding program here, which later led to
the development of his much acclaimed high-input, high-yield
varieties. The valley, with its 225,000 hectares of irrigated
wheat, became one of Mexico's most productive breadbaskets.
But for the farmers and families in the Yaqui Valley, the Green
Revolution highway is more and more becoming a road to perdition.
The sustainability of the valley, which was once highly regarded
for its advanced agro-technology and biological richness, is now in
question. When drought hit the region in the late
1990s/early-2000s, the degraded soils were unable to cope with
water shortage. In the 2003-2004 crop cycle, less than a quarter of
the land in the Yaqui Valley could be planted. The abundant use of
pesticides is also taking its toll.
In the early 1990s, a Mexican researcher found extremely high
levels of pesticides in samples from children in the Yaqui Valley.
A follow-up study was published in 1998 by Dr. Elizabeth Guillette,
an anthropologist and research scientist from the United States.
She compared children from the farming communities of the Yaqui
Valley, where a wide mix of pesticides is applied 30 to 40 times a
season, with those from a village in the Sierra Madre foothills,
where far fewer pesticides are applied.
Pictures of people drawn by 4 year old Yaqui
children. Pictures on the left by children living in the Sierra
Madre foothills, which are less exposed to pesticides; pictures on
the right children by from the Yaqui Valley that live close to
farming areas with high pesticide application rates.
[Thanks to Elizabeth Guillette]
The research team found the Valley children had poor hand and
eye coordination. The four and five-year-old children were below
the standard level of three-year-olds at such simple tasks as
catching a ball. One of Dr. Guillette's findings was particularly
disturbing. She asked the children to draw a person, a standard way
to measure a child's perceptual and motor abilities development.
The four-year-olds from the foothills could draw a complete person.
But of the Valley children, most four-year-olds just scribbled, and
the five-year-olds only drew a head and a line or a circle and a
In the heartland of the Green Revolution, farmers and their
families are losing out.
The only thing that still blooms here is the algae.