Challenges cities face

When very many people move into a city, they need food, water, energy and housing. This puts pressure on everything, and strains the city's infrastructure (roads, pipes, power lines).

Problems the chapter lists:

• narrow, badly kept roads;
• unplanned housing areas with poor water, sanitation, power and rubbish collection;
• more and more vehicles;
• rising temperatures from 'heat islands' (city areas that trap heat).

Air pollution has a measure: the Air Quality Index (AQI). It combines pollutants such as particulate matter (tiny dust), carbon monoxide and sulphur dioxide into one number.

The safe limit is 50. The National Capital Region often records over 400. That is eight times the safe limit (50 × 8 = 400), in a place where crores of people live.

Slums are overcrowded settlements with poor housing and little water, sanitation or other city services.

They grow near the edges of cities, beside railway tracks and near industrial areas, wherever there is empty land. Why? Because there is not enough affordable housing for everyone moving to the city.

Remember: slum dwellers support the city. Many do informal work:

• selling vegetables;
• domestic help;
• laundry;
• construction;
• plumbing.

Government schemes such as the Pradhan Mantri Aawaas Yojana provide affordable housing.

Bengaluru's water crisis shows how problems link together. The city has water shortages in summer and floods in the monsoon. Why?

• groundwater is overused;
• there is no rainwater harvesting;
• lake beds have been built on.

Bengaluru once had about 1,000 lakes. Fast growth cut them to about 200, and many are polluted by sewage and chemicals.

Lakes like Bellandur and Varthur got covered in foam, gave off toxic gases, and even caught fire.

Now non-profits, Resident Welfare Associations and local people are reviving the lakes:

• desilting (removing mud);
• repairing bunds (lake banks);
• clearing drains;
• planting native plants;
• putting fish back.