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nations, such as Costa Rica, Peru, and
the Philippines, have well-intended
laws that strictly ban harvesting of na-
tive trees, including the trees that
regenerate naturally on abandoned
fields. “But if you document that you
planted the trees, they become yours,”
she says. “This has created a perverse
incentive to prevent farmers from turn-
ing their land back into natural forest,
and to plant tree plantations instead.”
Figure 2: Biodiversity and species richness continue to increase for years after
farmland has been abandoned. ISBELL ET AL, NATURE 2019
in the atmosphere … to levels last seen
almost a century ago.”
That study, which elicited sharp criti-
cism from other researchers, called
for planting at least 6.6 million square
miles of degraded land not currently
used for urban or agricultural purposes.
More than half the planting would take
place in six countries that are, conveni-
ently, also major contributors to climate
change: Russia, the United States, Can-
ada, Australia, Brazil, and China.
Crowther calls it “the best climate
change solution available today,” with
the potential to remove 25 percent of
the carbon dioxide emissions humans
have added to the atmosphere. But crit-
ics have characterized the proposal as a
distraction from the immediate priority
of reducing greenhouse gas emissions.
They also questioned the suitability of
land in the study for reforestation.
“These plans have been developed by
scientists who do a lot of remote sens-
ing and don’t understand the social
context of why these lands are in tran-
sition, or if they are in transition,” says
Mark Ashton, a forest ecologist at the
Yale School of Forestry & Environmen-
tal Studies. “This is much more complex
than looking at a map and thinking you
can plant trees, without understanding
the human context around that land.”
forests under the Bonn Challenge — an
international reforestation initiative —
about 10 percent have committed to
restore more forest than they have land
to grow forests on. Many other coun-
tries have committed to restore an area
that’s less than half the abandoned
land they have available.
This haphazard approach persists even
though the estimated scale of land
abandonment is massive. China has
reported losing about 7,700 square
miles of agricultural land each year. The
United States has lost almost 98,000
square miles of farmland just from 1997
through 2018. And according to one
recent estimate, the European Union
could have up to 82,000 square miles
of abandoned farm land by 2040, or
roughly 11 percent of the area that was
being farmed at the start of the century.
Worldwide, a 2011 study in the journal
Climatic Change put the current area
of “recovering secondary vegetation,”
including old fields, pastures, and re-
covering forests, at 11.2 million square
miles of land — roughly triple the entire
land area of the United States — and
rising. But that number included lands
used and abandoned at any point over
the past 600 years. It was also based on
computer models.
The study came with major caveats
of its own: The authors could not de-
termine whether the available land is
publicly or privately owned. Moreover,
some lands that are now suitable for re-
generation could become much less so
as climate change advances. Measurements of actual landscapes
are still surprisingly difficult to make,
according to Robin Chazdon, a tropical
forest ecologist now retired from the
University of Connecticut. Satellites and
other remote monitoring technologies
cannot readily distinguish, for instance,
between a naturally regenerating forest
and a tree plantation.
The biggest caveat, though, is that cur-
rent government initiatives on degrad-
ed lands typically lack even rudimen-
tary planning. For instance, of the 48
nations that have committed to restore The current chaotic approach to aban-
doned lands often pushes land man-
agers in directions that do nothing for
either wildlife or climate change, says
Chazdon. For instance, many tropical
Grassroots
Vol 20
No 1
March 2020
Under certain cir-
cumstances, grass-
lands and range-
lands can prove
more resilient than
forests for carbon
storage, one study
found.
Elsewhere, climate and biodiversity ini-
tiatives often compete instead of sup-
porting each other, says Frans Schep-
ers, managing director of Rewilding
Europe, a nonprofit group working to
re-establish native landscapes across
Europe. “The mainstream response to
abandoned lands is, ‘We have to put
windmills and solar out there, or we
need to use biomass and burn materi-
als from our forests.’”
Even tree planting can become “a tech-
nological solution, a numbers game,
planting the wrong species, in a straight
line, and in areas where they wouldn’t
actually grow back on their own,” re-
sulting in “a huge waste of money.” It
makes more sense, he says, to regener-
ate natural forests as functioning eco-
systems, including large herbivores to
reduce fuel accumulation on the forest
floor and prevent wildfires.
Likewise, says Schepers, converting
abandoned pastures to forests based
on the simplistic notion that this will
automatically improve carbon storage
can end up harming species and cli-
mate alike. Not only do many plant and
wildlife species require open habitat,
but under certain circumstances, grass-
lands and rangelands can prove more
resilient than forests for carbon stor-
age, according to a 2018 study from the
University of California at Davis.
That’s because they store carbon large-
ly underground, where it is less vulner-
able in drought- and wildfire-prone
36