Biodiversity conservation has now become a primary concern of governments, NGOs, and the public. Recently, both terrestrial and marine conservation have relied on protected areas as the primary tool. Many NGOs and national leaders have supported setting aside 30% of land and oceans as protected areas by 2030 in what is known as 30 by 30 (Kubiak, 2020). What most species need is habitat and protection from exploitation. While protected areas in the form of parks on land and marine protected areas (MPAs) in the ocean can achieve this when large enough and enforced (Edgar et al., 2014), the same ends can be achieved in human used areas. If we include areas outside parks with intact habitat and protection from exploitation then 30 by 30 is too modest a goal, and we should aim for much higher levels of protection but may not need 30% in parks.

On land, human occupation and crop production has totally transformed landscapes so that many species simply cannot survive there, and parks have proven to be an effective mechanism both to protect habitat and limit exploitation (Dudley & Stolton, 2010). In the oceans, fishing changes ecosystems much less (see Figure 1) and provided that exploitation is regulated, perhaps all species can be maintained outside of no-take areas.

In the oceans, target species abundance has been reduced by 60–70% (Christensen et al., 2014) and nontarget species, particularly marine birds, mammals, and reptiles have often been greatly impacted. But no harvested marine fish and only 15 marine birds, mammals and fish have gone extinct, and none in the last 50 years despite major increases in fishing pressure. Major declines in targeted species have been associated with expanding industrial fisheries from 1950 to 1995. These declines have now been largely reversed and stocks are increasing where fisheries management is effective (Hilborn et al., 2020). The major biodiversity concerns in the ocean are now non-target species and vulnerable ecosystems such as coral reefs that are subject to a wide range of stresses including terrestrial run off, a warming and acidifying ocean, and, in places, overfishing.

Marine protected areas are particularly effective in protecting ecosystems that have easily defined boundaries such as coral reefs and estuaries. They preserve sedentary or fragile species, ecosystems, and breeding areas for marine mammals and birds. However, the major effect of marine protected areas is to relocate fishing pressure to areas that remain open to fishing and where the great majority of marine biota occur. Given that many species of most concern such as sharks, albatross, and turtles are very wide ranging, even very large MPAs may not protect them. MPAs also do not remove human impacts such as pollution, warming and ocean acidification, and exotic species invasions.

At a local scale, effectively enforced MPAs have been shown to increase abundance inside of reserves but there have been almost no evaluations of whether overall abundance of fish increases when areas outside MPAs are included (Ovando et al., in press). Theory suggests that allocating 10–30% of areas to MPAs will cause total abundance to increase only when stocks were heavily overfished prior to implementation (Hilborn et al., 2006; Ovando et al., in press) but most MPAs are in countries where overfishing is uncommon. Effective fisheries management promises to protect 100% of the area from overfishing and fishing practices that destroy habitats.

Protection of endangered nontarget species has typically been accomplished by modifying the fishing gear and how and when it is deployed (Hall & Mainprize, 2005) benefiting albatrosses, turtles, and dolphins. These methods have been effective, but many fishing fleets have not adopted them and thus there is a great potential for increasing biodiversity by universal use of these tools.

Much human use on land is largely transformative and dramatically reduces biodiversity. Agriculture and pastoralism cover an estimated half of the earth's surface. Crop production has the greatest impact on biodiversity, with near total loss of native vegetation and most other biota in some areas (Figure 1). Terrestrial protected areas, where consumptive exploitation is kept to a minimum, have been the primary tool for land-based conservation, and have been largely successful where enforced (Wuerthner et al., 2015). Maintenance of intact habitat and protection from exploitation are essential for the conservation of large carnivores, and mega-herbivores, and they also must be large enough to maintain sustainable populations and migrations within them (Wright & Mattson, 1996). However where at least some components of native terrestrial habitat, such as refuge habitat and some of the prey base, has been maintained and exploitation controlled, even wide ranging top predators such as wolves, bears and cougars have been able to recover and be maintained outside of parks (Chapron et al., 2014).

Preservation of representative native ecosystems as reference baselines requires strict protected areas. However, with 14.7% of the terrestrial surface currently protected (see https://www.protectedplanet.net), these areas can only cover some of the biota, so the remaining species that would have occurred outside the protected area before human use must be conserved there. Theoretically, parks could be placed strategically to minimize species left outside parks (gap analysis) (Margules & Pressey, 2000), but in practice most parks are situated for other reasons. However, this approach would be suitable for identifying optimal human-use areas for restoration in future (Pressey et al., 1997).

There is a vital need to expand research into conservation of biota in transformed landscapes while simultaneously improving food production, particularly where areas with the original native biota have been completely extirpated or are likely to be in the future, as in Africa (Kremen & Merenlender, 2018).

The major difference between terrestrial and marine systems is that in the former many types of human use, particularly crops and habitation, completely distort the food chain, altering all trophic levels. In contrast, marine ecosystems generally retain most of their food chain structure at least at low trophic levels when subject to managed fishing. Figure 1b illustrates there is relatively little change except at higher levels as a result of human harvesting. In contrast, biodiversity loss in even low-intensity agriculture outside a terrestrial protected area such as the Serengeti National Park in Tanzania is considerable and ranges from 80% to 90% (Figure 1b).

生物多样性保护现已成为政府、非政府组织和公众的首要关注点。最近，陆地和海洋保护都依赖保护区作为主要工具。许多非政府组织和国家领导人支持到 2030 年将 30% 的陆地和海洋划为保护区，即所谓的 30 乘 30（Kubiak，2020 年）。大多数物种需要的是栖息地和保护免受剥削。虽然以陆地公园和海洋保护区 (MPA) 形式存在的保护区在足够大并得到强制执行时可以实现这一目标（Edgar 等人，2014 年）)，在人类使用的区域也可以达到同样的目的。如果我们将拥有完整栖息地和保护免受开发的公园外区域包括在内，那么 30 x 30 的目标就太小了，我们应该以更高水平的保护为目标，但公园内可能不需要 30%。

在陆地上，人类占领和作物生产已经彻底改变了景观，因此许多物种根本无法在那里生存，而公园已被证明是保护栖息地和限制开发的有效机制（Dudley & Stolton，2010 年）。在海洋中，捕捞对生态系统的影响要小得多（见图 1），而且只要对开发进行监管，也许所有物种都可以在禁捕区之外得到维持。

在海洋中，目标物种丰度减少了 60-70%（Christensen 等，2014），非目标物种，尤其是海鸟、哺乳动物和爬行动物经常受到很大影响。但是，没有捕捞过的海鱼，只有 15 种海鸟、哺乳动物和鱼类灭绝，而且在过去 50 年中，尽管捕捞压力大幅增加，但没有任何一种。从 1950 年到 1995 年，目标物种的大量减少与工业化渔业的扩大有关。这些减少现在已基本逆转，在渔业管理有效的地方种群正在增加（Hilborn 等，2020）。海洋中的主要生物多样性问题现在是非目标物种和脆弱的生态系统，例如受到各种压力的珊瑚礁，包括陆地径流、海洋变暖和酸化，以及在某些地方过度捕捞。

海洋保护区在保护易于界定边界的生态系统方面特别有效，例如珊瑚礁和河口。它们为海洋哺乳动物和鸟类保护久坐不动或脆弱的物种、生态系统和繁殖区。然而，海洋保护区的主要影响是将捕捞压力转移到仍然开放捕捞和绝大多数海洋生物区系的地区。鉴于鲨鱼、信天翁和海龟等许多最受关注的物种分布范围非常广，即使是非常大的海洋保护区也可能无法保护它们。海洋保护区也不能消除人类的影响，如污染、变暖和海洋酸化以及外来物种入侵。

在地方范围内，有效实施的海洋保护区已被证明可以增加保护区内的丰度，但几乎没有评估包括海洋保护区外的区域时鱼类的总体丰度是否会增加（Ovando 等人，印刷中）。理论表明，将 10-30% 的区域分配给海洋保护区只会在实施前种群被严重过度捕捞时导致总丰度增加（Hilborn 等人，2006 年；Ovando 等人，出版中），但大多数海洋保护区位于过度捕捞并不常见。有效的渔业管理有望保护 100% 的区域免受过度捕捞和破坏栖息地的捕捞活动的影响。

对濒危非目标物种的保护通常是通过修改渔具及其部署方式和时间来实现的（Hall & Mainprize，2005 年），使信天翁、海龟和海豚受益。这些方法是有效的，但许多捕捞船队并未采用它们，因此通过普遍使用这些工具来增加生物多样性具有巨大潜力。

人类对土地的大量利用在很大程度上具有变革性，并大大减少了生物多样性。据估计，农业和畜牧业覆盖了地球表面的一半。作物生产对生物多样性的影响最大，一些地区的原生植被和大多数其他生物群几乎完全丧失（图 1）。将消耗性开发保持在最低限度的陆地保护区一直是陆基保护的主要工具，并且在实施方面取得了很大的成功（Wuerthner 等，2015）。保持完整的栖息地和保护免受剥削对于保护大型食肉动物和大型食草动物至关重要，它们还必须足够大以维持可持续的种群和迁徙（Wright & Mattson，1996 年））。然而，在至少一些本土陆地栖息地的组成部分，例如避难栖息地和一些猎物基地得到维护和开发控制的情况下，即使是狼、熊和美洲狮等范围广泛的顶级捕食者也能够恢复并维持在外面公园（Chapron 等人，2014 年）。

保护代表性的本土生态系统作为参考基线需要严格的保护区。然而，由于目前有 14.7% 的陆地表面受到保护（参见 https://www.protectedplanet.net），这些区域只能覆盖部分生物群，因此在人类使用之前本应出现在保护区外的剩余物种必须在那里保存。从理论上讲，公园可以战略性地放置以尽量减少留在公园外的物种（差距分析）（Margules & Pressey，2000 年），但实际上大多数公园的位置都是出于其他原因。然而，这种方法将适用于确定未来恢复的最佳人类使用区域（Pressey et al., 1997）。

迫切需要扩大对改造景观中生物群保护的研究，同时提高粮食产量，特别是在原始本地生物群已经完全灭绝或将来可能消失的地区，如非洲（Kremen 和 Merenlender，2018 年）。

陆地和海洋系统之间的主要区别在于，在前者中，人类使用的多种类型，特别是作物和栖息地，完全扭曲了食物链，改变了所有营养水平。相比之下，海洋生态系统在进行有管理的捕捞时，通常至少将大部分食物链结构保留在低营养水平。图 1b 说明除了人类收获导致的更高水平外，变化相对较小。相比之下，即使是在坦桑尼亚塞伦盖蒂国家公园等陆地保护区之外的低强度农业中，生物多样性的丧失也是相当可观的，范围从 80% 到 90%（图 1b）。