Attacks on aid workers are a horrific reality in a world where more and more people need help as a result of natural disasters, and where ongoing and new conflicts affect the lives of tens of millions of people.

Humanitarian workers are putting their lives at risk every day in some difficult and dangerous places. It is important that we remember them every time a crisis unfolds. We are well aware that it is ordinary men and women who are the first to respond when disaster strikes.

Local people and community workers are the first on the scene and deliver the vast majority of humanitarian help. When local help is not enough, regional and international organisations provide additional support.

Humanitarian needs are growing around the world because of the effects of climate change, migration from rural to the poorest urban areas, rising food and fuel prices, and continued social and economic upheaval in many countries. Despite the financial turmoil we are seeing in every part of the world, people continue to respond generously.

The number of humanitarian workers who are attacked in the course of their work continues to rise despite the independence and impartiality of humanitarian work. Ours is not a political agenda. Our aim is to get help to those people who need it most.

We are constantly appealing to people's best instincts when we ask them to support our work and it is in that spirit that our theme for this year's World Humanitarian Day evolved. It is People Helping People. We want to recognise that every act of kindness and support contributes to making our world a better place.

Every day in communities all over the world, people are helping each other, from those volunteering in shelters for the homeless to those supporting women and children who are abused as a weapon of war.

It is important that we recognise all the different ways in which people help. Some give money, others give time or ideas, or share skills and experiences. Through the campaign, we want people to tell us what they intend to do to help others.

We're lucky to have the support of the global performer Beyonce and the songwriter Diane Warren, who are donating a video for the song I Was Here, filmed in the United Nations General Assembly, to the campaign.

Beyonce is using her global reach to spread our message. As she says, now is the time to leave our mark on the world and show that we care.

Join our global movement of People Helping People. Get involved by volunteering in your own community or fund-raising for humanitarian work around the world. Sign up to our social media campaign at www.whd-iwashere.org.

Say ''I Was Here'' on World Humanitarian Day 2012.

Valerie Amos is the United Nations under secretary-general for humanitarian affairs.