Environmental impacts caused by introduced plants, animals and pathogens have a long history, but if the great Zhang Qian were alive today, it would not be so easy for him to bring in all kinds of animal and plant products. Most countries today have legislation to control the entry of foreign species and agricultural products, and carry out inspections at harbors and airports using all kinds of equipment and techniques.
偉大的張騫若身在今日，要帶進各種動植物產品可沒那麼容易。由於外來物種與病菌造成環境衝擊的歷史長久，因此現代國家都立有防堵法令，港口、航空站也都設有關卡，以各種設備、手段過濾外來物種與農產品。