Tag: forest degradation

Can deep learning help us save mangrove forests?

Object-oriented classification of fused Sentinel images can significantly improve the accuracy of mangrove land use/land cover classification.

Mangrove forests are an essential component of the coastal zones in tropical and subtropical areas, providing a wide range of goods and ecosystem services that play a vital role in ecology. They are also threatened, disappearing, and degraded across the globe.

One way to stimulate effective mangrove conservation and encourage policies for their protection is to carefully assess mangrove habitats and how they change, and identify fragmented areas. But obtaining this kind of information is not always an easy task.

“Since mangrove forests are located in tidal zones and marshy areas, they are hardly accessible,” says Dr. Neda Bihamta Toosi, postdoc at Isfahan University of Technology in Iran working on landscape pattern changes using remote sensing. In a recent study in the journal Nature Conservation, together with a team of authors, she explored ways to classify these fragile ecosystems using machine learning.

Comparing the performance of different combinations of satellite images and classification techniques, the researchers looked at how good each method was at mapping mangrove ecosystems.

“We developed a novel method with a focus on landscape ecology for mapping the spatial disturbance of mangrove ecosystems,” she explains. “The provided disturbance maps facilitate future management and planning activities for mangrove ecosystems in an efficient way, thus supporting the sustainable conservation of these coastal areas.”

The results of the study showed that object-oriented classification of fused Sentinel images can significantly improve the accuracy of mangrove land use/land cover classification.

“Assessing and monitoring the condition of such ecosystems using model-based landscape metrics and principal component analysis techniques is a time- and cost-effective approach. The use of multispectral remote sensing data to generate a detailed land cover map was essential, and freely available Sentinel-2 data will guarantee its continuity in future,” explains Dr. Bihamta Toosi.

The research team hopes this approach can be used to provide information on the trend of changes in land cover that affect the development and management of mangrove ecosystems, supporting better planning and decision-making.

“Our results on the mapping of mangrove ecosystems can contribute to the improvement of management and conservation strategies for these ecosystems impacted by human activities,“ they write in their study.

Research article:

Soffianian AR, Toosi NB, Asgarian A, Regnauld H, Fakheran S, Waser LT (2023) Evaluating resampled and fused Sentinel-2 data and machine-learning algorithms for mangrove mapping in the northern coast of Qeshm island, Iran. Nature Conservation 52: 1-22. https://doi.org/10.3897/natureconservation.52.89639

Poison ivy an unlikely hero in warding off exotic invaders?

Dozens of studies have looked at the effects of Japanese knotweed on natural communities in Europe and North America. Yet Bucknell University professor Chris Martine still felt there was something important to learn about what the plant was doing along the river in his own backyard.

“The more time I spent in the forests along the Susquehanna River, the more it seemed like something was really going wrong there,” said Martine. “In addition to the prevalence of this single invasive species, it looked like the very existence of these forests was under threat.”

What Martine noticed was similar to what local nature lovers and biologists with the Pennsylvania Natural Heritage Program were also starting to see: these forests, specifically those classified as Silver Maple Floodplain Forests, were not regenerating themselves where knotweed had taken a foothold.

In a new study published in the open access Biodiversity Data Journal, Martine and two recent Bucknell alumni conclude that Japanese knotweed has not only excluded nearly all of the native understory plant species in these forests, but it has prevented the trees already established in the canopy from leaving behind more of themselves.

“If you were to fly over these forests, or even look at a Google Earth image, you’d see a nice green canopy along the river consisting of mature silver maples, river birches, and sycamores,” explained Martine. “But below that canopy there is almost nothing for tens of feet before you reach an eight-to-twelve-foot-tall thicket of knotweed. Few new trees have been able to grow through that in the last 50-60 years and our surveys found that seedlings of these species are quite rare.”

The authors suggest that as mature trees die of natural causes over the next several decades and are not replaced, these systems will shift from tree-dominated riverbank habitats to “knotweed-dominated herbaceous shrublands” incapable of supporting a rich diversity of insects, birds, and other wildlife. Loss of trees in these habitats could likely also lead to riverbank erosion and increase the severity of flood events.

The few places where knotweed has not taken over offer a bit of hope, however, from an unlikely hero: poison-ivy, which Martine calls “perhaps the least popular plant in America.”

“What we see in the data is that poison-ivy often trades understory dominance with knotweed. That is, when knotweed isn’t the big boss, poison-ivy usually is. The difference is that whereas knotweed knocks everyone else out of the system, poison-ivy is more of a team player. Many other native plants can co-occur with it and it even seems to create microhabitats that help tree seedlings get established.”

The prevalence of poison-ivy in these sites didn’t go unnoticed by undergraduate Anna Freundlich, who collected most of the plant community data — more than 1,000 data points — in a single summer as a research fellow.

“Anna developed a pretty serious methodology for avoiding a poison-ivy rash that included long sleeves, long pants, gloves, duct tape, and an intense wash-down protocol,” said her research advisor, “and even after crawling through the plant for weeks she managed to never once get a rash.”

Martine cautions against too much optimism regarding the chances of one itch-inducing native plant saving the day, however.

“Righting this ship is going to require eradicating knotweed from some of these sites, and that won’t be easy work. It will take some hard manual labor. But it’s worth doing if we want to avoid the imminent ecological catastrophe. These forests really can’t afford another half-century of us letting knotweed run wild.”

Freundlich is a now pursuing a Master’s degree in plant ecology at the University of Northern Colorado. Lead author Matt Wilson, a Bucknell Master’s student at the time of the study who analyzed the dataset, now works for the Friends of the Verde River in Cottonwood, AZ.

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Original source:

Wilson M, Freundlich A, Martine C (2017) Understory dominance and the new climax: Impacts of Japanese knotweed (Fallopia japonica) invasion on native plant diversity and recruitment in a riparian woodland. Biodiversity Data Journal 5: e20577. https://doi.org/10.3897/BDJ.5.e20577

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About Japanese knotweed:

Japanese knotweed is considered to be one of the toughest, most damaging and insidious plants in the world. Native to East Asia, the species has already established successfully in many parts throughout North America and Europe, where it can easily grow and invade private properties and homes. It is hardy enough to penetrate patios, house foundations and concrete. Given it spreads easily and can grow underground to a depth of 3 metres with a horizontal range of up to 7 metres, it is extremely difficult to eradicate and its treatment requires special attention. To find advice on recognition, hazards and treatment, you can check out The Ultimate Japanese Knotweed Guide.