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 — also 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.
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, with 60 percent of that decline occurring in the last 40 years,” Mateos explained. Furthermore, local species richness has declined by 40 percent over the past 150 years.
Mateos believes nature in itself is a thing of great value. Through its ecosystems, nature provides an estimated $125 trillion of benefits in the form of food, water, medicine, and other resources. Biodiversity is critical to ensuring the function and resilience of these ecosystems. To connect the dots: biodiversity is therefore central to clean air and water and the preservation of our food sources through seed banks, pollinators, and fisheries. Our health and livelihoods depend on the preservation of biodiversity.
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.
Ecosystems are made up of a diversity of animal, insect, 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 really a key message in Mateo’s talk: the best approach is not to 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, 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 interaction networks between communities. A resilient meadow has a greater abundance of network interactions, with a higher number of “strong links.” The same is true below ground: for soil communities, “the higher the complexity, the higher the functional resilience.”
For his own research, 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 Mateos, this seemed to be the perfect place to study the long-term impacts of ecological disturbance.
Examining an undisturbed site and a disturbed one, and looking at both above ground plant communities and below ground soil communities, 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.” 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.
But 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 ecological function.
The network interactions between plants and fungi in the soils were dramatically different. In the degraded, 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.
Mateo’s research has implications for global ecosystem restoration. Essentially, we may be restoring ecosystems on a superficial level, so these systems may not support future biological diversity or be resilient to future shocks.
To increase the resilience of restored ecosystems at a more rapid rate, Mateos called for sequencing whole genomes of recovering species to understand their adaptation potential. The idea is to select critical species with high genetic diversity and adaptation potential and strategically insert them into recovering ecosystems. This process could involve finding populations of species in a landscape with high-functioning genomes and using those seeds to help restore ecological balance in degraded landscapes.
Mateos envisioned designing assemblages of high-performing plant communities and targeting them for tough environments in cities, or to help recovering forests or other ecosystems at a landscape scale.
“We need to imagine long-term what the landscape will look like in 400 years.” Our future ecosystems must be “resilient to climate change, biodiverse, self-sustaining, provide ecological services, and last forever.”