Climate change is widely recognized as a “threat multiplier.” From the United Nations to the G7 to the US Department of Defense, there is emerging consensus that climate change poses risks to both human and natural security through a variety of complex and interrelated channels. The extent of those risks, and how they connect to armed conflict, however, remain widely debated.

We face the greatest environmental challenges ever relating to climate change, biodiversity, land use, and more. Humans are driving 1 million species to extinction, according to a report by the UN-backed Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Some $44 trillion of annual global economic product that depend on nature are in jeopardy. Fires have ravaged large swathes of the Amazon—Brazil and Bolivia in particular—and Australia.

Humanitarian need is increasing. Crises are becoming more complex through the interactions between climate change, disasters, and conflicts. Not only are humanitarian crises on the rise, but the nature of crises is changing, largely due to climate change-driven extremes such as floods, droughts and typhoons. Over 90 percent of disasters are believed to be related to climate.

In 2003, a scabies skin disease outbreak affecting mountain gorillas in Bwindi Impenetrable National Park was traced to people living around the national park—people with limited access to basic health and social services. To protect the people and wildlife of this special park, we launched Conservation Through Public Health (CTPH), an NGO that promotes biodiversity conservation by enabling people, gorillas, and other wildlife to coexist harmoniously through improved health and wellbeing.

Last summer, I stood on a cliff 100 feet above the Madre De Dios River, in Southern Peru near the Bolivian border, to watch the rosy gift of an Amazon sunset. It was quiet, in a tropical rainforest way, with the light clamor of parrots, macaws, and cicadas. Then, a peke-peke motorized canoe broke through the soft din. It arrived from the east, carrying a new supply of diesel fuel for the gold miners who were prepping the generator that would operate a suction-pump and dredge for gold across the river and around the bend. Before nightfall, the fuel ignited the baritone of a diesel generator. It moaned all night and all day, barely stopping. In subsequent days, instead of a light clamor of birds and primates, the thrum of a gold mining operation seemed like all I could hear.

For some time, it has been clear that a global population imbalance is emerging. High income countries, including nearly all of the Americas, Europe, and most of East and parts of South and Southeast Asia, have seen a dramatic, sustained fall in fertility. Already, this is resulting in shrinking labor forces and the oldest mean age populations seen in history. At the same time, the low income countries and even some lower middle-income countries—mainly in Africa but also in Central America, the Middle East, and parts of South and Southeast Asia—continue to have relatively high fertility. This is now, and even more in the coming decades, producing fast-growing labor forces and relatively young populations.