We are facing a planetary emergency caused by interdependent biodiversity loss and climate change. Whilst climate change is the third-most important driver of biodiversity loss, it also interacts with and exacerbates other drivers. At the same time, climate change and biodiversity loss share many common anthropogenic drivers, including the overexploitation of natural resources, unprecedented energy consumption and transformation of land-, freshwater- and seascapes. They also reinforce each other: increased atmospheric greenhouse gas (GHG) concentrations lead to global warming, altered precipitation regimes, frequent extreme weather events, and oxygen depletion and acidification of aquatic environments, which adversely affect biodiversity. Reciprocally, changes in biodiversity affect the climate system, especially by affecting the nitrogen, carbon and water cycles. Phytoplankton in particular play a crucial role in climate regulation, and their reduced growth due to ocean acidification could trigger catastrophic climate change. Finally, biodiversity loss weakens the climate adaptation capacity of ecosystems and human societies. These interactions generate complex feedback cycles with increasingly pronounced, less predictable and potentially irreversible outcomes. Under current trends we risk crossing cascading tipping points in the earth system.

The goals of climate change mitigation and adaptation and reversing biodiversity loss are strongly synergistic: nature is a vital ally against climate change. Actions to attain these goals separately, while overlooking their intertwined and mutually reinforcing nature, are likely to fail. In the worst case, actions directed at tackling one can hinder the solution of the other. The energy sector is key here; intensified renewable energy provision is a crucial action for climate change mitigation, which, if poorly planned, could adversely affect nature and biodiversity. Whilst most scientists and policy-makers now recognise the need for an integrated approach, research communities as well as governance bodies (UNFCCC/IPCC vs. CBD/IPBES) dealing with climate change and biodiversity remain somewhat distinct. The recent joint IPCC-IPBES report emphasised that this functional separation can entrain incomplete understanding of the interconnectedness of the two crises, thus missing opportunities to exploit the synergies and minimise the trade-offs in tackling them.

Among the important synergistic actions are nature-based solutions: actions to protect and restore nature that also tackle climate mitigation and adaptation. Halting and reversing the loss and degradation of natural ecosystems will be crucial for biodiversity protection as well as climate change mitigation, with large adaptation co-benefits. Sustainable agriculture and forestry can improve adaptive capacity, enhance biodiversity, increase carbon storage in farmland and forests, and reduce greenhouse gas emissions. But these measures can only succeed in tandem with ambitious reductions in GHG emissions; they rely on longevity, and a narrow focus on rapid carbon sequestration is likely to backfire.

There are also potential trade-offs. Measures narrowly focused on climate change mitigation and adaptation can have direct and indirect negative impacts on nature and nature’s contributions to people. To limit global warming to 1.5°C and avoid disruptive climate change, anthropogenic GHG emissions must reach net-zero by 2050. This clearly requires a major transition from fossil-fuel dependence to large-scale renewable energy deployment, as well as reduced and more efficient energy use. However, renewable energy expansion requires significant land assets and mineral extraction, and could, if poorly managed, come at high cost to valuable ecosystems.

Planting bioenergy crops in monocultures over large tracts of land is detrimental to ecosystems. Studies indicate that the biodiversity footprint of bioenergy is the highest of all renewable energy options, and that its benefits for power consumption can be overturned by its environmental costs. Biofuel feedstock cultivation affects biodiversity via land-use change, overexploitation, pollution, and other factors. Increased demand for forest biomass is harming biodiversity via more intensive forestry. Forestry measures such as afforestation in ecosystems that have not historically been forests, and reforestation with monocultures, can contribute to climate mitigation but are often detrimental to biodiversity without clear benefits for adaptation.

The production of wind energy, hydropower, solar PV, and electric vehicles also involves potential trade-offs for biodiversity, which should be taken into account from the outset. Solar plants can have high land requirements, modify local ecosystems, and lead to the conversion of natural habitat or increased pressure for agricultural intensification. Frequent collision with wind turbines and transmission lines could put vulnerable migratory species of birds and bats at risk. Dams impact freshwater ecosystems, leading to abrupt disconnection of water, sediment and life. Mining for minerals used in wind turbines, PV systems and electric car motors and batteries can adversely affect natural ecosystems, as can the disposal of decommissioned solar panels, motors and batteries.

Yet renewable energy, along with reduced and more efficient energy use, remains a priority for mitigating climate change in ways that benefit biodiversity. Insufficient progress on cutting GHG emissions through these means is prolonging fossil fuel use, and increasing reliance on geoengineering options such as negative emission technologies (NETs) to compensate for the ensuing emissions. The role of NETs in mitigation pathways to net zero by 2050 has been enhanced in recent IPCC reports, risking potentially greater impacts on nature while also jeopardising decarbonisation of the economy. Another risk is the later inclusion of more intrusive geoengineering options such as Solar Radiation Management (SRM) with possibly irreversible impacts on nature.