THE DIRT

The United Nations has declared the next 10 years the Decade on Ecosystem Restoration. This builds on the European Union’s recent commitments to biodiversity protection, including the restoration of 15 percent of its ecosystems. The New York Declaration on Forests — which is a result of the United Nation’s 2014 Climate Action Summit and has been endorsed by 200 governments and other groups — aims to restore 350 million hectares of forests by 2030. Another initiative is the 30 by 30 forests, food, and land challenge, which calls for reforestation on a global scale, also by 2030.

In a Zoom lecture sponsored by Harvard University Graduate School of Design (GSD), David Moreno-Mateos, a restoration ecologist and an assistant professor of landscape architecture at GSD, asked: “Are we ready to restore the planet?”

The trends on global biodiversity aren’t good. As humans degrade or destroy an increasingly large share of the Earth’s ecosystems, extinction rates have tripled in the past 100 years. “Vertebrate populations have declined 58 percent in the last 40 years,” Moreno-Mateos explained. Furthermore, local species richness has declined by 40 percent in most developed countries over the past 150 years.

Moreno-Mateos believes nature itself is a thing of great value. Nature provides an estimated $125 trillion of benefits in the form of food, water, medicine, and other resources through its ecosystems. Biodiversity is critical to ensuring the function and resilience of these ecosystems. To connect the dots: biodiversity is then central to clean air and water and the preservation of our food sources through seed banks, pollinators, and fisheries.

The challenge is that “ecosystem restoration is a long-term process.” In a review of scientific studies on some 3,000 restored ecosystems, research has shown that after 150 years, restored ecosystems are 70 percent less diverse and 40 percent less functional than undisturbed ecosystems.

Land-based ecosystems are made up of a diversity of animal, insect, fungi, and plant species, with specific carbon, soil, and water characteristics. There are specific levels of nutrients, including phosphorous, organic matter, and nitrogen. These elements all interact in particular ways. Given all the complexity, “ecosystem restoration has limited effectiveness.”

So this was perhaps the key message of Moreno-Mateos’ talk: the best approach is to not degrade incredibly complex ecosystems. There is still too much about their functions we don’t understand, and it’s nearly impossible to recreate their dense networks of interactions.

But if an ecosystem has been disturbed, Moreno-Mateos sought to find out: what happens over the long-term? What can be done?

Species diversity results in community composites. Think of a meadow, a community of plants that thrives together. There are interaction networks within those communities and between communities. A resilient meadow has a greater abundance of network interactions, with a higher number of “strong links” — “that is species that interact more strongly.” The same is true below ground. Amid soil communities, “the higher the complexity, the higher the functionality, and, likely, the resilience.”

For his own research, Moreno-Mateos started with the assumption that ecosystem degradation reduces genetic diversity. In southwest Greenland, Norse farmers settled two sites some 650 years ago. Archeologists discovered each village had about 100 people who farmed hay for cattle. To Moreno-Mateos, this seemed to be the perfect place to study the long-term impacts of ecological disturbance.

Examining an undisturbed site and a disturbed, former agricultural site, and looking at their above ground plant communities and below ground soil communities, Moreno-Mateos found “both sites had a similar amount of plant communities (35 species in the disturbed site and 34 in the reference site), but the compositions were totally different. In the disturbed site, one plant community dominated.” Moreno-Mateos also discovered the former agricultural sites had more nutrients because the Norse would add manure to the hay fields, which meant more nitrogen and phosphorous.

There was another key finding: the original, undisturbed site had more “mutualistic interactions.” The degraded site had more “pathogenic interactions.” This fit his hypothesis: “loss of biodiversity means more pathogens” and loss of function and resilience.

This was proven through the very different network interactions between plants and fungi in the soils in each site. In the formerly agricultural landscape, there were 15 plant species and just 37 fungi species, creating 62 links. In contrast, in the ecologically-healthy, undisturbed site, there were 12 plants and 76 fungi that created 148 links. This means networks in disturbed sites are more vulnerable to change.

Moreno-Mateos’ research could have implications for global ecosystem restoration. He believes restoration ecologists must “first understand how the complexity of ecosystems re-assembles over hundreds of years, and then find species that play critical structural and functional roles in the assembly process and use them in the restoration process.”

To increase the resilience of restored ecosystems at a more rapid rate, Moreno-Mateos called for sequencing whole genomes of species in recovering populations to understand their adaptation potential. This process would help identify populations of target species whose genomes have the best chance to adapt to ongoing global change.

The idea is to select species with critical ecological roles that come from populations with the highest adaptation potential and strategically insert them into recovering ecosystems. This process would involve finding populations of species in a landscape with high-functioning genomes and using those seeds to help restore ecological balance elsewhere.

Moreno-Mateos envisioned designing assemblages of high-performing plant communities and targeting them for tough environments in cities or for recovering forests or other ecosystems at a landscape scale.

“We need to imagine what landscapes will look like in 400 years.” Our future ecosystems must be “resilient to climate change, biodiverse, self-sustaining, provide ecological services, and last forever.”