Climate change is pushing Brazil’s farmland out of agricultural suitability range
A new study, published this week in Nature Climate Change, finds that warmer and drier climatic conditions in Brazil are changing the agricultural productivity of one of the world’s largest bread baskets.
Central Brazil leads the world in production of key staple crops including soybeans and corn, but those crops depend on a stable climate. Deforestation to expand such agricultural production is a counterproductive strategy, as it not only accelerates global warming, but also causes changes to the regional climate that can drastically impact crop yields.
The study, led by Dr. Ludmila Rattis, Assistant Scientist at Woodwell Climate, modeled changes to precipitation and temperature along Brazil’s Cerrado-Amazon frontier—a region responsible for half of the country’s agricultural output. The results show that already 28% of agricultural lands are no longer in an optimal climatic range, and that percentage will shoot up to 74% by 2060 as the region gets hotter and drier. The Cerrado in particular, Dr. Rattis says, will feel the effects of reduced agricultural productivity.
90% of Brazil’s agriculture is rainfed, which makes droughts, heatwaves, and other climatic interruptions a major economic risk. When the temperature gets warmer, plants grow faster, which releases more water vapor into the air from their leaves as a byproduct of photosynthesis. But if there isn’t a steady supply of soil moisture available to replace water lost through transpiration, productivity declines.
That difference in moisture is called the vapor pressure deficit (VPD) is a way of determining how thirsty the air is in a region. Dr. Rattis’s study found that over the past two decades, agricultural land has been expanding into areas of higher VPD.
With cropland pushing into less-than-optimal land, and deforestation exacerbating drought, agricultural intensification practices are becoming less feasible on existing cleared land. Practices like double-cropping corn and soy in one season are common, but require farmers to take advantage of the full length of the rainy season. With climate change, however, rainy seasons are starting later and dry seasons are more intense, requiring a lot more moisture to make up the deficit when the rains do come. If farmers can no longer plant two crops in one season, the pressure to deforest additional land to make up for lost profits will increase.
“If you don’t have the time you invest in more space,” says Dr. Rattis.
Irrigation isn’t necessarily a sustainable solution when roughly 70% of Brazil’s electricity comes from hydroelectric power, and the country’s rivers and groundwater supply depend on maintaining existing hydrology.
Professor Paulo Brando, an ecosystem scientist at the University of California, Irvine and co-author on the paper, describes how Brazil’s agricultural status quo is untenable.
“The current production system in the region may be reaching its full climatic potential,” Brando says. “Not part of this study, but it is clear from a growing body of research that a change in food habits and a reduction in food waste could help alleviate some of the pressure.”
According to Dr. Rattis, the key to successfully adapting Brazilian agriculture to a warmer climate lies in restoring and preserving native vegetation on the landscape—reducing the pressure on farmers to deforest and finding ways for forests and agriculture to share the land.
“Forests act like air conditioners for your crops. Farmers need to understand that deforesting in the face of climate change is like getting rid of your air conditioners before an upcoming heatwave,” Rattis says.
Mountain and polar groups seek urgent COP26 decision
As climate talks in Glasgow head into their second week, Woodwell Climate Research Center joins mountain and polar groups at COP26 calling for more consideration of the dire global impacts that will result from the loss of glaciers, ice sheets, and permafrost should governments not take greater action.
These research, environmental, and Indigenous organizations span the global “cryosphere” (snow and ice regions), from the poles to the high mountain Asia “Third Pole.” They believe that the poor understanding by governments of the real implications of the cryosphere poses a dangerous issue for climate goals. As a matter of urgency, the groups are asking COP26 to approve a decision point mandating the UNFCCC to arrange a day-long meeting, or “Cryosphere Dialogue,” at the next inter-sessional climate conference, scheduled to take place in Bonn in June 2022.
“For too long, our planet’s frozen elements have been absent from the climate debate at the UNFCCC, even though their crucial role in determining the future for more than a billion people and our climate is becoming ever more clear,” said Dr. Martin Sommerkorn, IPCC SROCC author, of the WWF Arctic Programme. “The UNFCCC must urgently create space for Parties and stakeholders to discuss actions to be taken in response to this cryosphere crisis.”
The groups note that despite the dire consequences noted in the IPCC’s August report there has never been a full discussion of the irreversibility of projected changes in the cryosphere at climate talks. In contrast, the UNFCCC has held Dialogues on oceans and lands.
Dr. Rachael Treharne from Woodwell Climate Research Center explained, “Thawing Arctic permafrost makes carbon that has been locked in the deep freeze for millennia vulnerable to release into the atmosphere. It’s critical that international mitigation policies address this catastrophic regional and global hazard.”
“Negotiators may think they know about melting ice caps, but what they don’t realize is that the impacts are essentially permanent on human timescales, and catastrophic for humanity,” noted Dr. Robert DeConto, a leading researcher with one of the groups, the Scientific Committee for Antarctic Research (SCAR). “Once the collapse of the West Antarctic Ice Sheet begins, it will be effectively impossible to halt,” agrees Jonathan Bamber, Director of the Bristol Glaciology Centre and a multiple IPCC author.
Pam Pearson, Director of the International Cryosphere Climate Initiative, which is hosting a Cryosphere Pavilion at the conference, said. “The questions by governments during discussion of the latest IPCC report last week underscore that this issue needs more than a 15-minute presentation.”
“The polar regions are no longer an early warming signal for climate change,” concludes Professor Dame Jane Francis, Director of the British Antarctic Survey. “Instead, they are now a driver of climate change and this reality needs to be better understood.”
The other organizations and institutions include the International Centre for Integrated Mountain Development (ICIMOD), the International Arctic Science Committee (IASC), Grantham Institute at Imperial College, Bolin Centre at Stockholm University, and the National Snow and Ice Data Center at University of Colorado Boulder.
Black spruce are losing their legacy to fire
Although evolved to thrive in fire-disturbed environments, a recent study shows more frequent fires are threatening black spruce resilience
For the past five to ten thousand years, black spruce have been as constant on the boreal landscape as the mountains themselves. But that constancy is changing as the climate warms.
A recent study published in the Proceedings of the National Academy of Sciences, led by Dr. Jennifer Baltzer, Canada Research Chair in Forests and Global Change at Wilfrid Laurier University, found that shifts in wildfire regimes are pushing black spruce forests to a tipping point, beyond which the iconic species may lose its place of dominance in boreal North America.
Synthesizing data from over 1500 fire-disturbed sites, the study showed black spruce’s ability to regenerate after fire dropped at 38% of sites and failed completely 18% of the time—numbers never before seen in a species evolved to thrive after fire.
The Stabilizing Feedback of Black Spruce
“They almost look like a Dr. Seuss tree.” says Dr. Brendan Rogers, an Associate Scientist at Woodwell and co-author on the PNAS study. He’s referring to the way black spruce are shaped—short branches that droop out of spindly trunks. Clusters of small dark purple cones cling to the very tops of the trees. Black spruce forests tend to be cool and shaded by the dense branches, and the forest floor is soft and springy.
“The experience of walking through these forests is very different from what most people are accustomed to. The forest floor is spongy, like a pillow or waterbed,” Dr. Rogers says. “It’s often very damp, too, because black spruce forests facilitate the growth of moss and lichen that retain moisture.”
However, these ground covers can also dry out quickly. Spruce have evolved alongside that moss and lichen to create a fire-prone environment. It only takes a few days or even hours of hot and dry weather for the porous mosses to lose their moisture, and the spruce are full of flammable branches and resin that fuel flames up into the tree’s crown.
Black spruce need these fires to regenerate. Their cones open up in the heat and drop seeds onto the charred organic soil, which favors black spruce seedlings over other species. The organic soil layers built up by the moss are thick enough to present a challenge for most seedlings trying to put down roots, but black spruce seeds are uniquely designed to succeed.
Dr. Jill Johnstone, Affiliate Research Scientist at the University of Alaska Fairbanks, who also contributed to the PNAS study, compares it to a lottery system that black spruce have rigged for millennia.
“After fire, anything can happen,” says Johnstone. “But one way to make sure you win the lottery is to buy a lot of tickets. Black spruce has the most tickets. It has the most number of seeds that are the right size to get roots down into mineral soil, and so it tends to regenerate after fire.”
Potential competitors like white spruce, Dr. Johnstone says, don’t disperse very far from standing trees so they only get a few lottery tickets. Deciduous species like aspen or birch have seeds that are too small to work through the thick organic layers—their tickets are faulty. So the fire lottery tends to perpetuate black spruce’s dominance in what’s known as a “stabilizing feedback loop”.
Hotter, Dryer Conditions are Inhibiting Black Spruce Regeneration
That stable loop has begun to break down, however. Black spruce just aren’t re-establishing themselves as frequently after fire. The study examined the characteristics of different sites to better understand what might be hampering regeneration success.
Sites that failed to regenerate with black spruce were typically drier than normal. They also tended to have shorter intervals between successive fires. Black spruce stands have historically experienced the kinds of intense, stand-replacing fires that burn through everything only once per century. This long interval allows the trees to build up a healthy bank of cones to release seeds the next time they burn. More frequent, returning fires short-circuit the regeneration process.
Increased burning also strips away more of that thick organic soil layer that favors black spruce, revealing mineral soils underneath that level the playing field for other tree species. The more completely combusted those organic layers are, the more likely spruce are to have competition from jack pine, aspen, or birch. Loss of black spruce resilience was more common in Western North America, which aligns with the fact that drier sites are more likely to lose their black spruce.
“Basically, the drier the system is, the more vulnerable it is to fire,” Dr. Baltzer says. “And these are the parts of the landscape that are also more likely to change in terms of forest composition, or shift to a non-forested state after fire. If climate change is pushing these systems to an ever drier state, these tipping points are more likely to be reached.”
For Dr. Rogers, it also highlights the real possibility of losing black spruce across much of boreal North America as the region warms.
“This is evidence that black spruce is losing its dominant grip on boreal North America,” Rogers says. “It’s happening now and it’s probably going to get worse.”
Losing Black Spruce Could Accelerate Permafrost Thaw
Landscape-wide ecological shifts from black spruce to other species will have complicated, rippling impacts on the region.
Of most concern is the impact on permafrost. In many parts of the boreal, those mossy soil layers that promote black spruce also insulate permafrost, which stores large amounts of ancient carbon. Replacing the dark, shaded understory of a black spruce forest with a more open deciduous habitat that lacks mossy insulation could accelerate thaw. Thawing permafrost and associated emissions would accelerate a warming feedback loop that could push black spruce to its tipping point.
Widespread loss of black spruce also has implications for biodiversity, particularly caribou species that overwinter in the forest and feed on lichen. Both barren-ground and boreal caribou, important cultural species for northern communities, are already in decline across the continent and would suffer more losses if the ecosystem shifts away from the black spruce-lichen forests that provide food and refuge.
Dr. Johnstone did point out some potential for black spruce to recover, even if initial regeneration post-fire is dominated by other species. Slower growing, but longer lived, conifers can often grow in the shade of pioneer deciduous species and take over when they begin to die off—but this requires longer intervals between fires for the spruce to reach maturity. There is also the possibility that more deciduous trees, which are naturally less flammable than conifers, could help plateau increasing fires on the landscape.
But both these hopes, Dr. Baltzer says, are dependent on getting warming into check, because deciduous or conifer, “if it’s hot enough, and the fuel is dry enough, it will burn.”
Giving carbon a home on the range
Adapting ranching practices in the US could increase carbon sequestered in the American West
Rangelands occupy more than three quarters of global agricultural land. Many of the world’s native grassland ecosystems have been converted to grazing land for livestock, altering their ecology and changing the flow of carbon on the landscape. However, these lands still have the potential to be a powerful carbon sink if properly managed.
On September 27 and 28, Woodwell Climate Research Center convened a workshop in collaboration with Montana State University (MSU) and Turner Ranches to open discussions on rangeland management in the United States. The workshop took place in Bozeman, Montana, and brought together scientists, ranchers, and conservationists to share their perspectives on rangeland ecology, carbon sequestration, fire management, and herd health, as well as anecdotes from careers spent on the range.
“Montana offers a great location for this conversation because the majority of the state is amazing rangeland including unique grassland and sagebrush steppe environments, in many cases privately held,” said Dr. Stephanie Ewing, an Associate Professor at MSU who co-organized the event. “And because we have a strong academic and extension community at MSU that has been engaged with rangelands and rangeland managers over time.”
Day one began with a series of presentations and panels meant to facilitate discussion about rangeland management. Sessions covered rangeland ecosystem services, rangelands in the American West, management for carbon sequestration, carbon markets, and tools for rangeland monitoring.
For Dr. Jennifer Watts, Woodwell Assistant Scientist, the discussions highlighted the vast untapped potential of rangelands to play a positive part in climate mitigation.
“There’s so much rangeland in the western U.S. and so there is a huge potential for improving ecosystems and improving carbon sequestration and storage,” Dr. Watts said. “But the public doesn’t perceive rangelands with the same reverence that we do with forests or other ecosystems. I think if we start to value them at the national level, and realize the potential for ecosystem services and climate mitigation, that could shape how policy is going to move forward.”
The following day, attendees made site visits to two ranches in the area—Red Bluff Ranch, run by MSU, and Green Ranch, owned by Turner Enterprises—for a hands-on look at the topics they had discussed the day before. They examined soil pits, dug into the grass, and talked about different land management styles.
For Senior Scientist Dr. Jonathan Sanderman, the trip into the field was a catalytic moment in the workshop.
“After just a few hours on the ranches, I felt like a lot of people had lightbulbs go off about how long-term management has affected certain parts of land more than others, and how that feeds back to the soils,” Dr. Sanderman said.
One theme that emerged from the workshop was the need for more and better information on how rangelands could be included in carbon markets. While there was interest from landholders in participating, very few knew enough to get started. Drs. Watts and Sanderman hope future collaborations will allow them to dig deeper into the topic with ranchers.
“A well-functioning carbon market can provide climate benefits and an additional revenue stream, enhancing the economic resilience of ranching communities,” Dr. Sanderman said. “Quantifying and monetizing carbon sequestration from improved grazing management is still in its infancy. This means there is a lot of confusion and few agreed upon standards; but, it is also an opportunity to shape policies and design programs that benefit people and the environment.”
It also became evident that, while many ranchers were interested in carbon storage on their lands, what mattered more to them was the possibility of integrated benefits from holistic range management. Improving carbon storage in the soils can improve water management, nutrient retention, and other ecosystem services.
“Carbon is something that brings it all together,” Dr. Watts said.
Imagining Earth’s most probable futures
New climate education initiative portrays the warmer worlds we are likely to see this century, in hopes of preventing them
One point five—most readers will recognize that number as the generally accepted upper limit of permissible climate warming. With current temperatures already hovering at 1.1 degrees Celsius above the historical average, the race is on to hit that target, and the likelihood that we will surpass it is growing. Even if we do manage a 1.5 degree future, that’s still warmer than today’s world, which is already seeing devastating climate impacts.
So what will it actually feel like to live in a 1.5 degree world—or a 2 degree one, or even 3? The Probable Futures initiative has built a tool to help everyone imagine.
Building a bridge between science and society
Probable Futures is a newly launched climate literacy initiative with the goal of reframing the way society thinks about climate change. The initiative was founded by Dr. Spencer Glendon, a senior fellow with Woodwell Climate who, after investigating climate change as Director of Research at Wellington Management, noticed a gap in need of bridging between climate scientists and, well… everyone else.
According to Dr. Glendon, although there was an abundance of available climate science, it wasn’t necessarily accessible to the people who needed to use it. The way scientists spoke about climate impacts didn’t connect with the way most businesses, governments, and communities thought about their operations. There was no easy way for individuals to pose questions of climate science and explore what the answers might mean for them.
In short, the public didn’t know what questions to ask and the technical world of climate modeling wasn’t really inviting audience participation. But it desperately needed to. Because tackling climate change requires everyone’s participation.
“The idea that climate change is somebody else’s job needs to go away,” Dr. Glendon says. “It isn’t anybody else’s job. It’s everybody’s job.”
So, working with scientists and communicators from Woodwell, Dr. Glendon devised Probable Futures—a website that would offer tools and resources to help the public understand climate change in a way that makes it meaningful to everybody. The site employs well-established models to map changing temperatures, precipitation levels, and drought through escalating potential warming scenarios. The data is coupled with accessible content on the fundamentals of climate science and examples of it playing out in today’s world.
According to the initiative’s Executive Director, Alison Smart, Probable Futures is designed to give individuals a gateway into climate science.
“No matter where one might be on their journey to understand climate change, we hope Probable Futures can serve as a trusted resource. This is where you can come to understand the big picture context and the physical limits of our planet, how those systems work, and how they will change as the planet warms,” Smart says.
Storytelling for the future
As the world awakens to the issue of climate change, there is a growing group of individuals who will need to better understand its impacts. Supply chain managers, for example, who are now tasked with figuring out how to get their companies to zero emissions. Or parents, trying to understand how to prepare their kids for the future. Probable Futures provides the tools and encouragement to help anyone ask good questions about climate science.
To that end, the site leans on storytelling that encourages visitors to imagine their lives in the context of a changing world. The maps display forecasts for 1.5, 2, 2.5, and 3 degrees of warming—our most probable futures, with nearly 3 degrees likely by the end of the century on our current trajectory. For the warming we have already surpassed, place-based stories of vulnerable human systems, threatened infrastructure, and disruptions to the natural world, give some sense of the impacts society is already feeling.
According to Isabelle Runde, a Research Assistant with Woodwell’s Risk Program who helped develop the maps and data visualizations for the Probable Futures site, encouraging imagination is what sets the initiative apart from other forms of climate communication.
“The imagination piece has been missing in communication between the scientific community and the broader public,” Runde says. “Probable Futures provides the framework for people to learn about climate change and enter that place [of imagination], while making it more personal.”
Glendon believes that good storytelling in science communication can have the same kind of impact as well-imagined speculative fiction, which has a history of providing glimpses of the future for society to react against. Glendon uses the example of George Orwell who, by imagining unsettling yet possible worlds, influenced debates around policy and culture for decades. The same could be true for climate communication.
“I’m not sure we need more science fiction about other worlds,” Glendon says. “We need fiction about the future of this world. We need an imaginative application of what we know.” Glendon hopes that the factual information on Probable Futures will spark speculative imaginings that could help push society away from a future we don’t want to see.
For Smart, imagining the future doesn’t mean only painting a picture of how the world could change for the worse. It can also mean sketching out the ways in which humans will react to and shape our new surroundings for the better.
“We acknowledge that there are constraints to how we can live on this planet, and imagining how we live within those constraints can be a really exciting thing,” Smart says. “We may find more community in those worlds. We may find less consumption but more satisfaction in those worlds. We may find more connection to human beings on the other side of the planet. And that’s what makes me the most hopeful.”
‘Summer of extremes’ briefing helps meteorologists connect extreme weather events to climate change
The summer of 2021 has been a summer of extremes. Catastrophic wildfires, drought, flooding and deadly heat waves are all signals of a warming climate, but the nature of that connection is often not well understood by the public. To help deepen understanding of the links between extreme weather and climate change, Woodwell hosted a briefing last week for a group that is always thinking about the weather: meteorologists.
The briefing was led by meteorologist Chris Gloninger of KCCI 8 Des Moines, who moderated a Q&A with Woodwell senior scientist Dr. Jennifer Francis and Assistant Scientist Dr. Zach Zobel. Dr. Francis and Dr. Zobel provided attendees with insight into how weather events, like the recent hurricanes Henri and Ida or flash flooding in Tennessee for example, are exacerbated by climate change.
Meteorologists, tasked with preparing local communities for changes in the weather, are uniquely positioned to communicate the role of climate change in weather patterns to a broad public audience. According to Dr. Francis, meteorologists are “often the only scientists that people come into contact with.” Which means they have a valuable opportunity to shape people’s perception of weather events as a consequence of climate change.
For Dr. Zobel, a meteorologist by training himself, one of the best ways to make those connections is by highlighting the specific elements of extreme events that the science shows are clearly linked to warming.
“Rather than focus on the storm itself, focusing on the features within the storm that climate models and observations show are clearly going to increase,” Dr. Zobel said. He cited the all time record for the amount of rainfall in one hour in New York that was broken during Henri. Heavy bursts of precipitation are likely to become more common with climate change, as a warmer atmosphere can hold more water vapor.
Meteorologists joined the briefing from across the United States, and were interested in the best ways to communicate climate science across diverse audiences, some of which might not be familiar with or accepting of climate science. Dr. Francis used the example of farmers in the Midwest who have reported more persistent weather conditions—longer droughts or storms—affecting their crops.
“If we can take that and link it back to how we think climate change is starting to cause more persistent weather patterns, that is something we can talk to them about that is really affecting how they do their business, how they live their lives, and is certainly something they are seeing every day,” Dr. Francis said.
Dr. Zobel also emphasized the need to communicate climate change in terms of personalized, individual impacts.
“Until we are able to do that, climate change may seem like a distant, far away problem,” Dr. Zobel said. “Once people see it’s affecting them locally they tend to re-evaluate.”
Riparian forests stand guard over Amazonian streams
In the remote headwaters of the Amazon, a small strip of forest—just 30 meters wide on either side of a stream—slices through a vast agricultural field. Although tiny, this forest stands as an important guardian of the health and biodiversity of the Amazon Rainforest.
In many places, riparian forests along the edges of streams and rivers are the last remaining forests on a landscape largely converted to agriculture. Brazil’s forest code requires a permanent protection area be left on the banks of waterways to buffer the effects of land use change on downstream ecosystems. But how effective are such small slivers of forest in the face of widespread landscape change? A trio of papers from Woodwell’s Tanguro Ranch research station in Mato Grosso, Brazil shows that even small forests can have big impacts on biodiversity and nutrient transfer.
Maintaining the ecosystem highway
Rivers act as highways through the forest, carrying species, nutrients and organic matter across the landscape. Trees play an important role in regulating those roadways, both drawing up water and nutrients and depositing organic matter in the form of leaves, seeds, and fruit. Clear the forest, and the traffic patterns for those nutrients will change.
Dr. KathiJo Jankowski, a research ecologist at the United States Geological Survey, conducted research with Woodwell on the question of whether maintaining riparian buffers successfully mitigated that change.
“Are streams now processing terrestrial materials differently? Are they processing carbon differently? And are they processing nutrients differently?” Dr. Jankowski asks. “We are interested in these questions, both in terms of how they affect stream food webs, and how they affect downstream ecosystems.”
She waded through the streams at Tanguro Ranch, collecting data—dissolved oxygen levels, leaf litter, temperature measurements—to answer these questions. When she compared data from agricultural streams with riparian buffers to intact forests, she found only subtle shifts in basic ecosystem functions. As long as those buffer forests remained, the streams mostly continued to flow as they always had.
“It provides good evidence that they are doing their job,” Dr. Jankowski said. “It highlights the importance of protecting those buffers because they are constantly under threat from people wanting to develop the land or simply not wanting to restore buffers that have been illegally removed.”
Preserving aquatic and terrestrial diversity
One difference Dr. Jankowski did observe, however, was in the amount of leaf litter present in the streams. Less overall vegetation on the landscape led to less organic matter in agricultural streams, a small change that can impact the wider food web.
Ecologist and researcher from the University of Brasília, Dr. Nubia Marques was conducting complementary research around the same time as Dr. Jankowski, but her research focused on the animals that rely upon the ecosystem functions Dr. Jankowski was studying. Tiny macroinvertebrates—crustaceans or insects that feed on stream organic matter—are found in most aquatic ecosystems, and their presence can indicate the overall health of a system.
According to Dr. Marques, degradation of riparian forests tends to simplify macroinvertebrate communities. Changes to available food resources impact species that rely on specific food more strongly than generalist species. Three taxonomic orders, Ephemeroptera, Plecoptera and Trichoptera (EPT) which include species like mayflies, stoneflies, and caddisflies, are particularly sensitive to disturbances.
“Many macroinvertebrates in the EPT orders cannot survive in sites of intense disturbance, so their absence may indicate that the health of the stream is not doing well when compared to similar streams that have not been disturbed at all,” Dr. Marques says.
Dr. Marques examined overall species composition, as well as functional composition (the presence of different feeding groups) across forested and agricultural streams. Streams with buffers tended to have greater overall diversity and slightly higher abundance of EPT species than those without, though watershed-level clearing did cause drops in EPT species with or without buffers. Because macroinvertebrates form the base of the food web, changes in their abundance have the potential to ripple upwards to the species communities that feed on them.
Beyond preserving biodiversity inside the streams, riparian forests are also important habitat for terrestrial rainforest species. Biologist at the State University of Mato Grosso and researcher at the Amazon Environmental Research Institute, Dr. Leonardo Maracahipes-Santos conducted detailed inventories of the size and species of trees, shrubs and vines in each of the transects to understand how the riparian forests themselves differed between intact and agricultural watersheds.
“There are some visible differences, that if you know the species you can see right away,” Dr. Maracahipes-Santos says. “One difference I noted was that in the agricultural riparian forest you tend to see more gaps. Also there are some species along the edges that are known to be pioneer species, they signal some level of degradation or turnover.”
His analysis confirmed his observations. Riparian forests tended to differ most from the composition of intact forests at the edges, where niches had been opened for species that normally don’t occur in dense forest. Also, as seen with the critters in Marques’s study, some plant species were just not as resilient to disturbance and disappeared completely from agricultural landscapes.
Dr. Maracahipes-Santos’ work shows that, for all these little forests do, they themselves are vulnerable to the effects of fragmentation. Though the law establishes a minimum width for riparian forests, the amount of forest considered functionally intact may be much smaller, highlighting the need for wider buffers with softer edges leading into agricultural fields.
Protecting the headwaters protects the landscape
The three studies together also revealed landscape-scale changes took place in streams despite the presence of buffers. Dr. Jankowski found agricultural streams tended to be warmer on average and received more sunlight due to increased gaps in the canopy. With fewer trees to draw up water, stream levels were higher in agricultural landscapes as well. This tracks with Dr. Maracahipes-Santos’ findings—species sensitive to soggy soil were harder to find in the riparian buffers on agricultural land.
Dr. Jankowski’s experiment also introduced nitrogen and phosphorus into the stream systems, mimicking a fertilizer runoff event, to track how far the nutrients would flow. Tanguro is situated at the headwaters of the Xingu River, a major tributary of the Amazon, which means that anything added to the watershed here has the potential to affect the larger system downstream. Dr. Jankowski found that nitrogen traveled far downstream regardless of buffers. Multiply the effects of one nitrogen plume across the thousands of headwater streams in the Amazon watershed, and the impacts could potentially extend all the way to the Atlantic.
Despite this, riparian forests remain an important line of defense against pollutants and biodiversity loss. They will play a growing role in linking and protecting the Amazonian watershed as agricultural clearing continues. To play this part successfully, they will need support and protection of their own.