Text by William H. Thomas
Social Network Analysis and graphs by Chris Leberknight
I began working in New Guinea in 1988. My first teacher was a man named Tama. Tama was born and had spent most of his life in the heart of this island, roaming the forests at the headwaters of the Strickland River — a region of New Guinea that is still considered unexplored. He was a Hewa — a member of a group so remote that, when I met him, they were still being accused of cannibalism. Tama was about my age, but he couldn’t read or write. He did, however, have an encyclopedic memory, and that made him a marvelous naturalist. He knew these forests better than anyone else, and he had finally met the one guy in the world who seemed to care about it. From 1988 to 2005, I trailed Tama around these mountains writing down everything he could tell me.
I am interested in connections. I wanted to know how the people, birds, plants — you name it — that can be found here fit together into the ecological web that makes up this forest. Since in 1988 I didn’t own a computer, I was forced to use accounting ledgers to organize Tama’s teachings. I had 184 species of birds and nearly 300 trees, shrubs, and vines in accounting ledgers cross-referenced with notebooks and charts from our conversations. Eventually all of this migrated to a computer, but I remained frustrated with my inability to extract from the spreadsheets the dynamic world of pollinators and seed dispersal agents that resided in Tama’s head.
Then I discovered Social Network Analysis (SNA). SNA is typically used to map and visualize relationships among people. You have probably seen SNA diagrams that visualize the connections among users of social media, such as Twitter or Facebook. It has also been used to visualize complex subjects such as terrorist networks or environmental feedbacks. SNA visualizations make the key players or bottlenecks in a system explicit. SNA makes it easier for stakeholders to understand the system and where they will need to concentrate their efforts to affect it.
The minute I saw a social network diagram, I knew that this was my best hope for releasing Tama’s wisdom from my notebooks. Instead of people, I wanted to substitute birds and trees in the SNA network maps. Luckily, I found out that Chris Leberknight, one of my colleagues at Montclair State University in New Jersey, USA, was an expert on SNA, so we began to explore the use of SNA to visualize Indigenous environmental knowledge.
Indigenous knowledge is often presented as a simple inventory of local names for plants and animals. That does not do justice to the complexity of Indigenous understandings of ecosystem dynamics, and makes it difficult to translate Indigenous knowledge into effective conservation action.
Indigenous knowledge has a communications problem. Indigenous classification systems do not always easily map onto genus and species classifications. Indigenous knowledge is often presented as a simple inventory of local names for plants and animals. That does not do justice to the complexity of Indigenous understandings of ecosystem dynamics, and makes it difficult to translate Indigenous knowledge into effective conservation action. For instance, in 1989 the Coordinating Body of Indigenous Organizations of the Amazon Basin (known as COICA from its Spanish acronym) appealed to conservation organizations to build on the Indigenous knowledge base to conserve the Amazon. While the initial reaction was enthusiastic, almost thirty years later the conservation of the Amazon basin is far from having been secured, and successful partnerships with Amazonian Indigenous communities remain few and far between.
New Guinea’s forests present a unique opportunity for such partnerships. While the island is one of the world’s most significant centers of biodiversity, so much of New Guinea is only accessible by foot that most of its forests have not been surveyed. Fortunately, these forests remain in the hands of their Indigenous landowners, and Indigenous environmental knowledge is vibrant in remote areas.
Tama and I created an Indigenous knowledge database that describes the role birds play in seed dispersal in one of New Guinea’s most important tracts of forest — the headwaters of the Strickland River. Understanding the relationship between birds and trees will be a vital link in the conservation of these forests. If we want to have an impact, however, we have to make our data useful and available to all of the stakeholders in the conservation process. Only the most determined naturalists will wade through the data sets in my ledgers. Anyone interested in accessing Tama’s knowledge will be confronted with 286 trees cross-referenced with 184 birds and their roles as pollinators and seed dispersers. This dizzying array of possibilities is impossible to communicate because they get lost when buried in data tables that are guaranteed to bore both the professional conservationists and the Indigenous landowners whose cooperation you will need to develop a conservation plan. This is where SNA can help, as the network portrayed in Figure 1 shows.
Conservation is essentially a political process. One of the challenges is getting the interested parties together and agreeing on the facts, so that we can jointly craft and support a conservation plan. This can be especially difficult when people of varying cultures and educational levels are trying to work together. In my experience, the key lies in finding common ground and expanding the circle of trust among the participants. In terms of conservation planning, this often means identifying keystone species and building your plan around their needs. A keystone species is a species that plays a critical role in shaping its environment. Its actions help to determine the species composition of the community. Like the keystone in an arch, this species may seem rather insignificant. Yet it holds the ecosystem together, and without it the ecosystem may collapse. Creatures ranging from elephants to jaguars to hummingbirds have been identified as the keystone species in different ecosystems.
SNA is the perfect tool for identifying and visually portraying keystone species. Just as a social network map consists of clusters of friends, our ecological network map consists of clusters of birds and trees. Birds are the primary agents of seed dispersal in New Guinea, spreading seeds as they feed on the fruits from different trees. For this example, we limited our analysis to ground-dwelling birds that subsist on fruits that have dropped from the tree. To investigate the importance of the different bird species in dispersing seeds, we created a simplified network that connected all the birds that were observed eating fruit on the ground into a single network map.
Just as a social network map consists of clusters of friends, our ecological network map consists of clusters of birds and trees.
Once we created a map of the ground-feeding birds, we wanted to identify those birds that were the most important in the network. In terms of SNA, this is known as “centrality.” The degree of centrality is measured by computing the number of links connecting an individual to the network. A high degree of centrality implies greater and more direct influence. In the context of our ecological network, an individual bird’s degree of centrality indicates its influence on the ecosystem. This is based on how many trees it feeds on and which trees are entirely dependent on this bird for seed dispersal. A bird that eats the fruit of many trees exhibits a high degree of centrality and has a significant impact on the ecosystem because it is responsible for dispersing the seeds of many different trees. It is by definition a keystone species. Conversely, birds with a low degree of centrality are birds that are specialists. They do not visit many types of trees and do not share similar feeding habits with other birds.
After organizing our data, we chose to focus on the role of the Dwarf Cassowary (Cassowary bennetti) in this ecosystem. We thought this would be a good starting place to establish the common ground needed for a conservation planning dialogue. The Dwarf Cassowary is an iconic species in New Guinea, whose role in seed dispersal is recognized by both Western and Indigenous naturalists. Cassowaries are secretive, however, and their habits are best known to Indigenous hunters. In other words, a literature search was not going to produce much on Dwarf Cassowary feeding habits. Indigenous knowledge of the bird’s feeding habits, especially in an area that is considered unexplored, was our best bet for uncovering the role the cassowary plays in Tama’s forests.
As you can see from our SNA graphics of the cassowary’s role in seed dispersal, an SNA visualization is a dramatic improvement over a spreadsheet. Anyone looking at Figures 2 and 3 is immediately struck by how many plants rely on the Dwarf Cassowary for seed dispersal. Of the 335 vines and trees I have recorded, the cassowary acts as a dispersal agent for 260. SNA allowed us to extract this information from our database and produce attention-grabbing graphics. What’s more, not only can we portray the cassowary’s role as a keystone species (Figures 2 and 3), but we can also visualize the ecological collapse that would follow the bird’s removal from this ecosystem (Figure 4).
Because botanists have not systematically surveyed the headwaters of the Strickland River, tree names are given in Hewa. Although I believe that most of these trees are known to science, matching Hewa and scientific names is, in my opinion, unimportant in this context. This exercise is about creating common ground for conservation and developing the partnerships between Indigenous landowners and conservation organizations so that together they can take action. The Hewa have yet to experience the scenario depicted in Figure 5, but we have plenty of experience with localized extinction and the resulting frayed ecosystems. By combining SNA with Indigenous knowledge, we can portray the impact of the removal of a species or the removal of primary forest. This information, known by Indigenous naturalists and important to understanding tropical forests, is more than likely to be lost if it remains confined to a spreadsheet.
By combining SNA with Indigenous knowledge, we can portray the impact of the removal of a species or the removal of primary forest. This information, known by Indigenous naturalists and important to understanding tropical forests, is more than likely to be lost if it remains confined to a spreadsheet.
Does Indigenous knowledge hold all the secrets to conserving these lands? I doubt it. Yet it seems ill-conceived and arrogant to cast aside thousands of years of observations by skilled naturalists. Time is of the essence, and we now know that scientists are barely scratching the surface in their understanding of regions like New Guinea. While Indigenous knowledge remains vibrant and these areas remain biological treasures, we need to leverage this knowledge for conservation. SNA is a tool that can help Indigenous stakeholders communicate their knowledge — not just of one tree or one bird, but of an entire ecosystem. SNA allows us to paint a picture that describes the dynamics of what we are trying to conserve. It may not be a perfect picture, but it is one that can galvanize support for conservation.
William H. Thomas, PhD, is Director of the New Jersey School of Conservation. He has conducted research in Papua New Guinea since the late 1980s, developing a “Forest Stewards” program to conserve the island’s wild lands. UNESCO has recognized his work as a “Best Practice.”
Chris Leberknight is Associate Professor of Computer Science at Montclair State University. His work blends social network analysis with computational methods to identify patterns, features, and dynamics in ecological networks that help shed light on biodiversity conservation issues.
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