Ecologically friendly agriculture doesn't compromise crop yields
University of British Columbia
Diversification includes practices such as growing multiple crops in rotation, planting flower strips, reducing tillage, adding organic amendments that enrich soil life, and establishing or restoring species-rich habitat in the landscape surrounding the crop field.
"The trend is that we're simplifying major cropping systems worldwide," says Giovanni Tamburini at the Swedish University of Agricultural Sciences and lead author of the study.
"We grow monoculture on enlarged fields in homogenized landscapes. According to our study diversification can reverse the negative impacts that we observe in simplified forms of cropping on the environment and on production itself."
The research, published in Science Advances, is based on 5,188 studies with 41,946 comparisons between diversified and simplified agricultural practices. Crop yield was in general maintained at the same level or even increased under diversified practices.
The enhanced biodiversity benefited
pollination and pest regulation by natural predation. It also improved water
regulation and preserved soil fertility. Diversification, however, had variable
effects on climate regulation. In some cases, it increased greenhouse gas
emissions.
"By
bringing together so much data, this work powerfully shows the potential for
diversified farming to maintain productivity while reducing environmental harms
and sustaining biodiversity and ecosystem services," says Claire Kremen at
the University of British Columbia and co-author of the study.
"However,
we need to tune these techniques to specific crops and regions, maximize these
benefits and reduce trade-offs that otherwise occur. Much more investment is
needed to support adoption of diversified farming practices, through research,
management incentives and extension programs."
Increasing biodiversity is assumed to enhance yields and ecosystem services such as pollination, pest regulation by natural enemies, nutrient turnover, water quality and climate change mitigation by carbon sequestration.
Although much
research has been invested to explore this, outcomes of diversification had not
previously been synthesized. Further, the focus had mainly been diversification
of crops and vegetation. Diversification of soil organisms is seldom
recognized.
"An
important next step is to identify which practices and conditions that result
in positive or negative climate mitigation, and to avoid practices that give
negative impacts," says Sara Hallin at the Swedish University of
Agricultural Sciences and co-author of the study.
Studies
where yield had been examined together with one or more other ecosystem
services were few but still many enough to analyze occurrence of win-win,
trade-off and lose-lose situations. Win-win outcomes between yield and another
service dominated with 63 % of the cases, but all other possible outcomes (i.e.
representing tradeoffs between yield and ecosystem services) were also
represented.
Many
of the tested diversification practices are in use already today, but can be
more widely adopted and combined both on and off the crop field.
How
can we diversify our farming systems?
There
are many ways to increase diversity both on and off the crop field. Farms can
add crop species to crop rotations, or grow crops together in the same field
with intercropping. Flowering crops provide pollen and nectar for pollinating
and predatory insects. Farms can also support below-ground biodiversity by
mulching crop residues and adding manure or minimizing soil disturbance by
reducing tillage.
