Writing in Newsweek, Mary Robinson calls on cities to defiantly lead on global challenges like climate change and migration, especially when national leaders spurn their responsibilities.

The sight of the Statue of Liberty never fails to stir any visitor to New York. For over a century, it has symbolised this city’s openness to the world, the welcome it has given to people from the four corners of the Earth, and the value it places on the contributions they make to their new home.

“Give me your tired, your poor, your huddled masses yearning to breathe free” inscribed on the statue’s base, has a humane lyricism which continues to resonate and inspire me today as I attend the Global Mayors Summit hosted by the City of New York.

Cities thrive on immigration, diversity and pluralism. We see this across the United States and the wider world, from New York to London, Istanbul to Johannesburg, Beijing to Brasilia. Cities can and should be the crucible for an inclusive and empowering globalisation that drives sustainable economic growth and offers a model of integration for wider society.

Yet the political and economic climate is challenging. Bold leadership is required from mayors and civic authorities to fulfil cities’ potential and confront the threat of populist isolationism.

More than 65 million people worldwide have been forced from their homes as a result of conflict, climate change, poverty and a myriad of other factors.

In the past few weeks alone, we have seen the physical, social and economic devastation wrought on American cities and vulnerable communities across the Caribbean by Hurricanes Harvey and Irma, and the death and destruction caused by monsoons across South Asia. We know from previous experience, such as Hurricane Katrina in 2005, that some people affected will be displaced from their homes forever.

Many of these displaced people are drawn to cities, but the capacity to integrate these new arrivals in a manner consistent with their human rights and dignity is often woefully inadequate – reflecting an equally inadequate response from political leaders.

This illustrates the profound injustice of climate change: those who are most vulnerable in society, no matter the level of development of the country in question, will suffer most. People who are marginalised or poor, women, indigenous communities and slum dwellers will be disproportionately affected by climate impacts.

One year ago, the countries of the world came together here in New York for the UN Summit for Refugees and Migrants. It was the first time the issues had been discussed together on this scale at the United Nations, and it signalled the international community’s acknowledgement that the unprecedented number of people on the move was a global challenge.

The summit culminated in the New York Declaration, where countries committed to essential guiding principles aimed at improving the world’s response to refugees and migrants. It also set in train the process for developing two Global Compacts – one for refugees, one for migrants – which are due to be agreed in 2018.

For millions of vulnerable people still braving the perilous waters of the Mediterranean Sea or stranded in squalid camps in Calais, Greece or Kenya, noble words at the UN only become meaningful when they are translated into real changes on the ground.

Moreover, the last twelve months have seen retrograde steps taken by countries or regions to which the world has traditionally looked for leadership.

President Trump has sought to more than halve the number of refugees that can be admitted to the United States this year alone, and repeatedly expressed his desire to ban refugees from certain countries from reaching these shores at all.

As Kofi Annan has said: “curtailing the US refugee resettlement programme… undermines the great values of a nation that has long championed humanitarian principles and human rights.”

But the past year has also borne testament to the irrepressible humanity of so many individuals, families and communities who have opened their doors and hearts to their fellow human beings in time of need. From privately-chartered boats rescuing migrants from the Mediterranean, to private sponsorship schemes in Canada enabling refugees to be safely resettled and integrated into communities, the resilience of global solidarity offers hope for the future.

Cities are at the frontline of this struggle. How they rise to the challenges of reception and integration can demonstrate the great benefits of economic pluralism, which is an essential tool in combating xenophobic and anti-migrant narratives.

Cities and their mayors can assert the principles of international cooperation even when national leaders wilfully spurn their responsibilities – for example the pledge of the Global Covenant of Mayors, including New York, Washington DC, Chicago, Los Angeles and Miami Beach, to continue to work to honour the Paris Agreement on climate change.

More of such leadership is needed in the future. To date, cities and mayors have not been sufficiently included in national and international debates where policy priorities are shaped. The Global Mayors Summit is a vital chance for their voices to be heard: to challenge intolerance, highlight success and inspire future generations.

Mary Robinson will address the Global Mayors Summit in New York on 18 September. Watch the livestream at 10:35 ET.