Aid vs. remittances

From Roving Bandit, who also gave us migration vs. microfinance, comes this equally striking chart:


That's right - private remittances outweigh the total of international development aid for a given year.

Is this related to resources? Well, it might be in the sense that the income-generating activities for migrants in developed countries might be less resource-intensive and environmentally unfriendly than in developing countries (I am thinking slash-and-burn agriculture, etc.). I’m not sure, though, and would be interested in any existing analysis of this.