This week’s massive earthquake and resulting tsunamis in South Asia are a tragic reminder of just how vulnerable we are — and how fragile are our defenses — when confronted by nature’s destructive powers. The human toll wrought by the catastrophe in Asia is incalculable. Tens of thousands have died as a result of the Earth’s momentary heaving, an estimated one-third of them children. Millions of people living in coastal areas that rim the Indian Ocean have lost relatives, their homes and their livelihoods to the ocean’s mighty swelling.

The death toll from the tsunamis in Asia ranks among the worst natural disasters in recent history. Heavily populated, impoverished coastal communities received no warning of the impending disaster and were hit hardest. For countless families in Sri Lanka, Thailand, Indonesia, India, Somalia and other tsunami-affected areas, it might have seemed that hope itself was swept out to sea.

Our hearts go out to our Asian and African neighbors, even as our hands ready for the task of helping them rebuild their shattered lives and communities. The first task is to bury the dead to prevent the contamination of drinking water supplies and the possibility of infection from water-borne diseases such as typhoid, diarrhea and hepatitis. With millions left homeless, and health systems in shambles in many of the worst-affected areas, urgent action is critical to prevent further loss of life in already exposed, impoverished, and isolated communities.

In the immediate aftermath of the disaster, the international community has responded generously with both resources and manpower. In the days ahead, we will call upon the world’s continued generosity as the full dimensions of the Asian earthquake-tsunami disaster becomes clearer. With half a dozen countries urgently in need of assistance, the task of providing clean water, sanitation, essential health care, food and shelter to millions of displaced people will represent one of the world’s largest-ever relief operations.

To meet this challenge and save the maximum number of lives, our assistance must be timely, well coordinated and targeted. The catastrophe in Asia will require an extraordinary relief effort coordinated across several countries and costing billions of dollars. My office at the United Nations will lead coordination efforts, maximizing resources in the most timely, effective, and efficient manner possible, working closely with the International Federation of the Red Cross/Red Crescent, international and national NGOs and local disaster response efforts.

As with any humanitarian crisis, securing access to the victims is of paramount importance. Many of the worst affected areas still are cut off from communications. UN-led relief teams, ably assisted by local and national relief experts and a plethora of international NGOs, must race against the clock to reach those in greatest need.

The cooperation of local and national governments is essential to this and many other relief efforts. We have been heartened by the Indonesian government’s decision to open access to UN workers in Aceh, an area previously closed to foreigners on account of political strife. We call upon all governments to ensure that the rights of those displaced by this disaster are respected.

The challenges are formidable, ranging from the financing and logistical coordination of immediate assistance to instituting some form of regional early warning system to mitigate the effects of future disasters. We have no time to lose. Earthquakes, tsunamis, floods and other phenomena wreak devastation for millions of people each year, many times more than the casualties caused by war and other conflicts. Add to this the threats posed by climate change, environmental degradation and uncontrolled urbanization, and the result is a humanitarian house of cards with potentially catastrophic consequences.

There are steps we can take today to mitigate the threat of future natural calamities. First, we must capitalize on the increased awareness and international goodwill resulting from the tragedy in Asia, and get serious about instituting disaster preparedness and risk reduction efforts.

Second, as a global community we should draw lessons from previous crises and set out a plan of action to mitigate the effects of future disasters. The World Conference on Disaster Reduction, set to convene in Kobe, Japan, next month, provides an excellent opportunity.

In Kobe, governments, NGOs and experts from around the world will set forth a 10-year plan for risk reduction that calls on local, national, regional and international authorities to strengthen their disaster preparedness.

— Jan Egeland is the emergency relief coordinator for the UN Office for the Coordination of Humanitarian Affairs.