The fourth point in Diamond's framework concerns friendly neighbors. As previously noted, according to Diamond, the Norse Greenlanders did not have very good relations with their neighbors the Inuit, which diminished trade between them. Additionally, as the weather became colder and icebergs increased, it was more difficult to get commercial ships in and out of Greenland, leading to a loss of support from their trading partners in Scandinavia. The Greenlanders had also missed the opportunity to trade with the North Americans. Since Scandinavia was the only "domestic" trading partner, the loss of trade from here had a very significant impact on the Viking people. The basic necessities they needed, such as wood and iron (which were useful in maintaining/creating their cultural identity) were lost with trade. Additionally, the Black Death that struck Norway in the mid-14th century (with trade coming from Norway, Scandinavia, Iceland, and then Greenland) created economic and political instability as it killed half the population Norwegian. This caused difficulties for Norway to send commercial ships. Additionally, Greenland's main export (walrus tusks) lost its value to foreign countries as sources of ivory began to come from Africa. The Greenlanders' decline in trade and "friendly neighbors" was one of the "ultimate factors behind the demise of the colony of Greenland" (Diamond, p. 267). McAnany and Yoffee believe that Diamond's view is one of two divergent views on why Greenland's trade relations have deteriorated. Another view more related to resilience thinking is that, instead of their trade stopping when their neighbors found trade elsewhere, it was due to a lack of interest in trade. As it was believed that "although ... middle of paper ...... people's roles are important, the tendency toward collapse and failure increases when the circumstances people find themselves in suddenly change . If the lands that the Norse owned within their own society overlapped, and perhaps even those of the Inuit, the Greenlanders would have had a better chance of surviving resiliently. The final point of resilience would be ecosystem services, in which Nordic Greenlanders would attempt to protect their environment and become more aware of their surroundings. If they appreciate the trees that have provided them with their resources and try to help in return by planting more trees, they will be more resilient in their society. There are many ways the Greenland Norse should reorganize themselves and become more resilient, but the Norse lived as long as they could in the circumstances they found themselves in and put themselves in before leaving the Greenland..