CINXE.COM

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "www.unep.org",cType: 'managed',cRay: '92a50e963edcf8f4',cH: 'LX5qHPP2r.fe.LVtzARLlZxj6YQKd4l3I4K1LU2nCFM-1743646513-1.2.1.1-dKzf7dwphGB.D7YvtFLOT8J8y78CKvKkTaoNBlpNRCKYUQuOCnu1vUQ29nP7_TW7',cUPMDTk: "\/zh-hans\/kexue-shuju?__cf_chl_tk=SAGiMgclc_n_TOQWDDikvcI.Sn61TjbzzkrpsRbKA8w-1743646513-1.0.1.1-WvWjtvVCUrZOSBJ_ju3qBAFJ8nB_Vh_prR3bHeenAF4",cFPWv: 'g',cITimeS: '1743646513',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/zh-hans\/kexue-shuju?__cf_chl_f_tk=SAGiMgclc_n_TOQWDDikvcI.Sn61TjbzzkrpsRbKA8w-1743646513-1.0.1.1-WvWjtvVCUrZOSBJ_ju3qBAFJ8nB_Vh_prR3bHeenAF4",md: "rabsSXmsNIuWfjJeuXE_FP.NIYcDonj_0iRhBYEIyHI-1743646513-1.2.1.1-uEWCRhioiAdhXkS2PmrEWUIRhzZNpqJizyX_o3hSu1pm1ayjLXFmnP03iKdMTRYkNSkmC7bVCJ6aVFkQhD9o.K7WyLXtO4HGnSI4cbkxpkhar.f3ohz.nZJQbAdZLZdR7tM9QVJRrHFAqd1zcOFuYl_A9f8a4y77l7N8DyHi01szr_gI5i2ULf.MqIm7Cv8qaMpGnpSe931QfVVLMaV3AZP1lFMgfDUJc2k8eLjnNu26xY5YFJ2iGVKT6wgc4uCu44nG5G2bD0qc5qJvdWQsY_7c3nQfI7cWoR1buxorf2BwkFVlanwEc3ejRPf4FCJPFDF_vWt4t30ULmg.qlJ7KSEvG5POy4lEfY1oFSP2RGiGOCvwKv3m5VOrjqTRpon9E896aYWw7oXjzfcLw_tnbAHnbIIGx4eVxuqcRXEs5.72qYoSuo3b6DwPUK8yXZWT_8yrzbZUbZBFe6ngqaMoEiZn4eHGjwbfaNauduoxRd7rWbT3.5dT0ifniD6dCGZoLZY5Q3j6thKAzm.hNIKzSku0k76aowvVc_yhnjaHmmr5BiXS0BWITSwvSeVYvElZRl.1M2d6FzCqBZBu2mtzVdEjIXl0lFPtmBZRgXYEf6ILVx3PxB0YHTKshNEW7UqLwSIEyRRYSDPlLhahiVCdXeN1.ucHvj61zAOpkzY6tEYG06VTC4xIiWG.4qEDP.tvg8sxVfsiwLUmDmMNMYfOG4QzMq4klQgvJJCa11cYgu36OF77uvDADW4Tx8gxQ6tuKXMhQZjyERncD2Lx0DrGfGC9WLRa_5MQOtTaCDGAeA702ovm9s5Q4T_vkXMne_fWUMwVjFjJd7GNk0B3.V58vMPWl74AthMVP1ZijnZ.7m_SC322.zGAgLbJdzeWUIZhXkpelJ91EoI1_mUmQ.3zhqWcWqH.n1g1Yu57SiaB1Hx6GHjHWLHxYC6sZkkFtN0yiX684aE7eOZOApDZfDrKJfCbTalrq7bIHFVf5Jrjy3.ww5n2JIsX7JlfeZe8pr65KjHRsIUrkePlRjKhT2XtPNAkFpDSIt3OVwa9_mEOoOa1UhqOYkehdjGlvlwEQ2TD7B9_tg0imDQzfrX6bjRCs9quSOeEmKLaddJIVBoHKWFhds5LBCM6oH0ZXIR7CwLdrKicnnWAs524j7RDlYnZRiBYuT.Cq9aUGvwMarkZ0PYXAZmH.h5pgHrZrcuW9R88adKYlcVNYo4ohNPPBpWJ5w",mdrd: "6wLiWliCA_NHAlhYif8AlhVI4pqvqsf7zCj1Rz9RvCE-1743646513-1.2.1.1-NulBGaQU1Le6z3gzT8KK0Jl3aiL5OBPUIruIcFYlJSxl51UxDQA.9..W8QqV.z_VqMiN8XQiXRhKovm1vDYbLOkn2b1XKz4kKxyicyicRLJvbyCoUNnF2QJGUmY0aZs2NLqMoWGR7ZeOw0Z1_zvZbyWCb5ZbWhUCroEyvvlbi09NlX3iAVO89vMLmf07ve5XptTNtIL9EhSp0MdDHLmKCF3waxThCjESyOEBqkJspSsVL2LBz.Oj652G4smNZfH8jBKd3Vud_LDqnQqY6PFfx.n0cKv8tJRiavYMV_erQQYKq2uAsRjXoVVMZ.C0iS2otytGQLMvQ9ZOEhrCf8lx2V1gG.mvO7qsIOahTkLfdPK8lCupI8YDISkT8j_Of3gPMylo36.Aa4sLe_sGebylruKKjMMWOBEdqYPqXtSAq1fKpMokqB69QveKBitZ0SQXA0uZtE1ThtHvdMmbRk0z6CgMFLkMd_3en6jyOTUs6pjbtMTWtHA09mbK3WfNPMlifr9rZSHNmY90boTjeQpgV.2FdcJCr_dYens_3KnxJscP0B1Ogf5VoFSnhr_R86Usd6giFiBdprWPExckKxulTZXtY7ZCctk27Nn_6sIPdW9yMJKpP789KwIjTbWmkBqRmiFrB0CChlXlf3OqVyim5MRqXopz2MJDXJn3Tm5axk41oW.Oo7Xyxq9jbg.zNxGWKA9T1LogaFf3NMmN8eay4HFDbyqhjIQx0J_UAhKoy7ghHGtc2xouxK3YbLwspVLF_dyhBDFETSktE3vXbPvB4dxEUyeV0th7N_ER9uQKpzzK6.emUWyU7UhzgnCMCq.P.1QjzgveFl4X_qRyWsKAFGRPCvOSvX9sgcgw_LSJX9GLV.0YrOoUhha7Lzm4VUVbcJirR42Z1UGmw9GhaKpK8gDe5yic0qlxMfmcYv5xNR72uR.KA9NnA.N9P1l4v2QaTnKDt23JIDvdosu0ICU_Dlmf8sD.s_jruN987q4dKDT8GlCa5uH2ZdvAIKCRrITKe8Qt5xycuHES8RD_8nAfdzJ9mbQpOu2JJQ_dxiN4BGZ7ZPSXzYVTseNj4OWjhDQXYKnSmUQn0gjuxfMIsNQyGJsTX32aVopt8tiLMCLxro_.YVgpUJ0yR8l.fnxJNOd0hNKK.C17iQKfF11v8QbG7B8RT37ko5gHgwtPSpO8HhiSumV3vWc7fv6EkK3uiE_1G0ZiUbGOS9C_aIJvNaCiTLKwG0Yi7xPZgTXRQM4JvpwVnYiXaKb56lJGuv7poMicnQnTmZVpoyxj29qko7hbrQGlaQMh473RRnfwbDxdLoe9oaCq1RWY.3fwk1.wi2zZaOUNXgDW.ih6LhcZDlxmDlPp9PrOk6yQdEeqEpPNqc9F5N8prCsGe596wkm_A7EEZhQtKG8VruQX4ytXBrShe7qZv0dZ4m4XBigqNiRYfo0mgdvLX7J8C_PHZp6xG0Hz.cSei39WKDPKpCunIJMDQ31njqIYJ6KZ92WQO3wnXMsrhG74nn_YxpGK7wVnl7lVft8HPlAHGwo8F59gmuumAPrg5nsEhpK3WSLA83gktoCTfWjI8VMgAjDw1hz_JeJkx5QeiZLq4d7lJg8jhNBBeuw4EKRA9czjEWJvpoGDhmn4KIEt67uUKxokj2Pabuci0YNjO7j2xeaZVMisS_06ZU9XUIIaERprANXVw6zVdWtN7CuRmNeE5d_l3EVXVn1VC8ti_c9dq74I5l5Kp9WMiCIArD.jUaOb_hwW2dl.XTMvDjFKvj99v.310MkQj7nFJbDtfNCUSXZzPGl0d2ZsY51HTs1g8.K_jaqvupXbpNbZpn40uhcp7cKIWlt9RauHHyiCKqDqgvUFOPMV9rPuZk6cwYauD4r.eyOMIBhibGRZ.EDo_6GR2Vyb02zeyJsf0Nnmbqlk4ENaMlQZHZuzT1hhYoU7ZDrxU_x8wlpVoIDQAeRaiwI23kEPvOquBM9kokKHDWKDWd_N9bMmHZRxI_zDMeaqfYHd9CbjWaElUYug4X8grMtxCv3viLXzicbqQsY4eRd8J3qYIc82rn1SAQ"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=92a50e963edcf8f4';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/zh-hans\/kexue-shuju?__cf_chl_rt_tk=SAGiMgclc_n_TOQWDDikvcI.Sn61TjbzzkrpsRbKA8w-1743646513-1.0.1.1-WvWjtvVCUrZOSBJ_ju3qBAFJ8nB_Vh_prR3bHeenAF4" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>