开头：
"Dear Esteemed Colleagues/Dear Friends,"
"In light of the pressing challenges we face today, I am writing to propose a collective initiative that we believe will have a positive impact on our society."
"As stewards of our environment, we have a responsibility to act now and address the critical issues that threaten our planet."
结尾：
"Together, we can make a difference. Let us join hands to implement these initiatives and create a sustainable future for all."
"We look forward to your support and participation in this endeavor. Together, we can make a difference."
"Thank you for considering our proposal. We are eager to work with you to bring these ideas to life."
这些开头和结尾的句子可以作为撰写英语倡议书的参考，根据具体内容和目标受众进行调整。
