Compounding of factors.
For example, if there is a net change of just 2% in the population per year. After 10 years, your population will be down 18%. After 20 years, down by 1/3rd.
It doesn't take a big effect compounded by time to big change.
Ducaholic wrote:Until they do have a published study stating otherwise I will stick to the man made interference as one of the most prominent reasons fewer ducks are coming to La.
I agree. It's a percent or two per year for the addition of millions of acres of corn. It's a percent or two per year for the reduction in rice production. It's a percent or two per year for habit rehabilitation and expansion up north. It's a percent or two for expanded flooded fields including corn.
5 factors shifting populations 1% per year further north and after 20 years, your population is down to 1/3rd of what it was.
I think it is manmade changes, but many small aggregate effects. More corn up north, more pressure down south, more wetlands in general up north for flood control, more rehab'ed wetlands, more warm water discharges, less harsh winter weather, less habitat down south, less rice down south, ...
The aggregate effect of many factors. Not one single one being the driver, but all contributing small but significant to the populations that stay north living longer, healthier, and more productive than their southern brethren.
