Urbanisation brings clear challenges, well shown by Rio de Janeiro (Brazil), where around a fifth of residents live in favelas such as Rocinha. These informal settlements occupy steep, sometimes unstable slopes, with overcrowded, poor-quality housing, limited sanitation, and historically high crime and gang- or drug-related violence; the city also suffers traffic congestion, air pollution and water pollution that put pressure on health and services. On the strength of this, the statement appears convincing.
However, the opportunities are equally real and explain why migrants keep arriving. Rio offers far more employment than the countryside — in tourism, the port, manufacturing and services — together with better schools, universities and hospitals, and the economic growth that comes from businesses clustering in a large market. Moreover, the challenges are not permanent: upgrading schemes such as Favela-Bairro have brought paved roads, sanitation, electricity and services to many favelas, and transport improvements have widened access to jobs, showing that good management can reduce the problems over time.
On balance, the challenges are most severe for the poorest residents and in the short term, but the continued in-migration shows people judge the opportunities to be worth it, and investment can steadily reduce the challenges. I therefore agree only to a limited extent: whether challenges outweigh opportunities depends heavily on how effectively the city is governed — with strong management, the opportunities can outweigh the challenges.