Originally Posted by
starlanet
I collected snail shells while enjoying the sun in Vancouver, then put them in my checked bag and visited Los Angeles, went thru LAX and IAD and arrived in Buenos Aires. I didn't have a small bag or recipient for the sand though. Now I'm happy I got "a piece" of Vancouver and I have it here till I get the chance to see this beautiful city again. Never though of it as harmful or dangerous or anything, and luggage is going to collect bacteria at the airports in a way or another.
Here's the problem, not all lifeforms or biological threats are visible. Those snail shells might well have contained all manner of microorganisms, bacteria, or viruses (both plant, animal infectious) that have natural balances in one climate and not in another. Single celled microorganisms are particularly prone to multiplying out of control in friendly environments, especially tropical ones.
If they get to South America and have no local offsets, they will flouish out of control..this happens with bacteria as easily as with rabbits (look at Australia's rabbit problems).
It's dangerous enough in the normal course of events..the stuff we pick up abroad and bring home in our bodies..the bacteria in india you get on your hand and the hand you use to open a door in canada several hours later..even the stuff of plant spores and pollen you get on your clothing walking outside in Estonia at the airport can enter Brazil later that day and fall of your clothes..it's uncontrollable.
But if you deliberately go and find something biological and move it elsewhere for something as fleeting as "posterity" you increase the risk immensely.