Global population growth is not slowing down fast enough. The problem is Africa. Just about everywhere else, fertility rates are (roughly) at or below replacement levels. But Africans still want, and have, big families. This is partly a matter of the imperatives of rural farming (where children are important sources of labor), partly poverty (where you have to overshoot because most of the children will not be around to support you in old age) and partly cultural drag (where men rule and children are sources of status). What to do???
Do everything we can to make universal access to contraception possible. Do everything we can to encourage urbanization. Do everything we can to help governments handle the challenges of urbanization (infrastructure, public health, sanitation, safety, education). Do everything we can to increase the education of women (so they have options other than submitting to the demands of men). Do everything we can do to encourage late marriage (since fertility falls precipitously after 30). Do everything we can to stimulate economic growth (since hope discourages youthful childbearing).
Then keep our fingers crossed. And keep trying.