Lord Palmerston owned more than 10,000 acres in Sligo, which he first visited in 1808. He changed systems of landowning and tried to rationalise estates, constructed a series of roads, planted hundreds of acres of grass to stabilise the sand, established a plant nursery at Cliffoney (as well as two schools, a Catholic church and a dispensary) and built a harbour at Mullaghmore. He spent over £1,000 per year between 1830 and 1841 on improvements, against an income from the estate of c.£3,500 per year.
Despite all these improvements, exceptional in their nature, Palmerston has to pack almost 2,000 people off to America in 1847 when the famine hits. This keeps the mortality rate low, but it reinforces the point that the Irish population isn't sustainable. Either they go overseas, or they starve.
Feeding 8 million people on imported food is EXPENSIVE, especially as steamships are just coming into service and long distance trade is still quite expensive.
Just to add to this: Palmerston's agent calculated the cost of outdoor relief in March 1847: "more than three fourths of the amount will be payable by your Lordship... it cannot fall much short of £10,000 for the next 7 months". In other words, the cost of relief was four or five times as much as the gross rent Palmerston had made per year from the land.