Just lately, I’ve been feeling guilty about writing my cousin Jem out of my life.  Mostly, I forgive and forget as fast as a labrador, but I’ve already forgiven Jem for heaps of things, including watching me eat three Alice B. Toklas brownies before he revealed the ingredients. I spent the next 24 hours in bed, seasick and dizzy and honing my fury. But I forgave. Or rather, forgot. I also forgave him when I was seriously ill and he pestered me to stop seeing doctors and visit a faith healer he’d heard about.

I resisted. As children, we’d sneak off on summer evenings to a neighbouring farm where tent revivals were held. Faith healers were the star attractions, and we felt innocent pride at the army of crippled, blind, deaf and disfigured people living in our small town, although the healer didn’t inspire much faith. His suit was stained with sweat, and when he shouted, his spit rained down on the rows of hopefuls. We called it ‘Holy Spit’ and choked on the thought. One night, Mr Piggott, the town’s blind piano tuner, was healed in front of our eyes. By the time our piano needed tuning in September, he was blind again, a miraculous detail that inclined me towards modern medicine.

The final rupture came many years later when I took my English husband home for my grandmother’s 90th birthday. Jem gave me a hug, said he was happy for me, but he sure hoped we weren’t going to procreate, then launched into a sermon on how over-population was dooming the planet. ‘Whoa,’ said the broody bride, and I pointed out that preaching zero population growth at a family reunion was bound to still the music and sour the wine. He was gone before we cut the cake.

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But 20 years on, my cousin’s obsession with the burgeoning population now haunts me. It began with some simple maths by David Attenborough in How Many People Can Live on Planet Earth? shown before Christmas. When he was born in 1926, there were two billion people on Earth. Now, there are nearly seven billion. In planetary terms, this has happened in the blink of an eye. By 2050, the world’s population will rise to more than 9½ billion and it will require two Earths to sustain it. Population growth is at the root of our environmental crisis. More people need more food, more water, more energy. Population control should’ve been the alpha and omega in Copenhagen, but environmentalists don’t want to go there. One reason is because when the West speaks of population control, it really means there aren’t too many of us, but too many of them. People who live in India.

In Africa. We want them to have fewer children in the same way we want welfare-dependents to have fewer children. But that’s unsayable, so we hide the truth and dwell on the side effects of too many people: urban sprawl, slums, rainforests demolished, polluted water, immigrants fleeing their parched homelands.

On this small island, we feel the inconvenience of over-population, but not the urgency. Our schools, hospitals and roads are too crowded, we can’t book a clown for little Hannah’s fifth birthday because there are more Hannahs than there are clowns.

Later on, a mountain of A*s won’t get Hannah into Cambridge, because there are now far more clever Hannahs. It’s maddening, but it’s not famine. Mr Attenborough is a worried man, but he believes we can still save the planet. All we have to do is educate girls. Educated women have careers, marry later and are content to have just one child. As an educated mother of one (I confess: I wanted more), I’m thinking about apologising to my estranged cousin, but first I’m going to join the Optimum Population Trust. I’m wary of faith healers, but I’m convinced that fewer folks is the best way to heal the Earth.