2022年12月英语六级第2套真题句子解析： "We have been in this cycle of environmental generational amnesia for a long time, where the baseline keeps shifting and we don't even realize what we're losing until it's gone. If we can get people to understand how much meaning and value can come from having more experiences with more wild forms of nature, then maybe we can stop this cycle and move toward conserving and restoring what we have left."

where the baseline keeps shifting and we don't even realize what we're losing until it's gone

在定语从句 "where..." 内部，"the baseline keeps shifting" 和 "we don't even realize what we're losing until it's gone" 是两套独立的主谓结构，由对等连词 "and" 连接，构成并列关系。前者陈述基线变化的客观事实，后者递进说明人们对这种变化的无知，两者在定语从句内形成分句级并列。

If we can get people to understand how much meaning and value can come from having more experiences with more wild forms of nature

该结构包含三层嵌套：主句层 "we can stop..."（层0），if 条件从句 "If we can get people to understand..."（层1），宾语从句 "how much meaning and value can come from..."（层2），介词宾语从句内的动名词短语 "having more experiences..." 可视为层3的非谓语嵌套。从句层层包含，构成典型的深层嵌套结构。

don't even realize what we're losing until it's gone

"not...until" 结构表达「直到…才…」的时间逻辑，强调主句动作在 until 所指时间点之前未发生。本句中 "don't even realize...until it's gone" 表示「直到（自然）消失了才意识到我们正在失去什么」，符合该结构的核心语义：否定词 don't 与 until 构成时间逻辑关联，realize 这个动作在 it's gone 之前未发生。

识别要点：1) 主句必须包含否定（not/never/don't 等）；2) until 引导时间状语（从句或短语）；3) 两者共同表达「在某时间点之前未发生、该时间点才发生」的语义。

常见陷阱：not 与 until 在句中出现但不构成时间逻辑关联（如分属不同语义层次），或 until 单独作时间状语但主句无否定（表示动作持续到某时间点，而非「直到…才…」）。遇到这些情况需排除。

本句应用："don't even realize" 是否定主句，"until it's gone" 是时间状语从句，两者构成完整的 "not...until" 主从句式，表达在消失之前一直未意识到的时间逻辑。

then maybe we can stop this cycle

"then" 在 "If...then..." 条件框架中作为连接副词，表示前后两个事件之间的逻辑推进或条件结果关系。本句中 "If we can get people to understand...then maybe we can stop this cycle" 构成典型的条件-结果序列：前句提出条件（让人们理解），后句通过 "then" 引出基于该条件的可能结果（也许能停止这个循环）。

识别要点："then" 在句中起承接作用，连接两个动作、状态或事件，通常出现在 "if...then..." "first...then..." 或 "and then" 等框架中，表示时间顺序或逻辑推导。

排除标准：1) "then" 单纯表示「那时/当时」作为时间状语修饰某个动作（如 "I was living in Beijing then"），不起连接作用；2) "then" 用作定语（如 "the then president"）或固定短语（如 "now and then"）。这些情况不属于连接或篇章标记用法。

本句应用："then" 承接 "If" 引导的条件从句，引出基于该条件的推论结果，体现条件-结果的逻辑序列关系。